chemistry ninth grade.pdf

CHEMISTRY Ninth Grade AUTHORS

EDITORS

AYHAN NAZLI DAVUT PIRAZ NUH ÖZDIN UĞUR HULUSI PATLI ALI RIZA ERDEM YENER EKŞI MUHAMMET AYDIN

NECMETTIN SENTURK MUSTAFA OZ MUHAMMET AYDIN

ZAMBAK PUBLISHING

LUMINA EDUCATIONAL INSTITUTIONS

Copyright © Zambak Yayýncýlýk ve Eðitim Gereçleri A.Þ. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form without the prior written permission of the publisher.

Digital Assembly

Zambak Typesetting & Design

Language Proofreader

Jessica TAMTÜRK

Page Design

Memduh SEYMAN Özkan BÖLE

Publisher

Zambak Yayýncýlýk ve Eðitim Gereçleri A.Þ

This book has been prepared for high school chemistry courses by Zambak Publishing and in collaboration with Lumina Educational Institutions, it was rearranged and designed according to the national curriculum of Romania. Chemistry is an interesting and fundamental branch of science. It gives us the chance to explain the secrets of nature. What is water? What do we use in our cars as fuel? What is aspirin? What are perfumes made of? These kinds of questions and their answers are all part of the world of chemistry. Chemists work everyday to produce new compounds to make our lives easier with the help of this basic knowledge. All industries depend on chemical substances, including the petroleum, pharmaceutical, garment, aircraft, steel, electronics industries, etc. This textbook is intended to help everyone understand nature. However, However, one does not need to be a chemist or scientist to comprehend the s implicity within the complexity around us. The aim of our efforts was to write a modern, up-to-date textbook in which students and teachers could glean concise information about basic topics in chemistry. Throughout the textbook, different figures, colorful tables, important reactions, funny cartoons, interesting extras, and reading passages have been added to help explain ideas. We hope that after studying along with this book, you’ll find chemistry in every part of your life.

Authors

Chapter 2

Chapter 1

Introductıon of

Chemistry

INTRODU INTR ODUCTIO CTION N . . . . . .. . . . . . .. . . . . .. . . 8

The Periodic Table INTRODU INTR ODUCTIO CTION N . . . . . . . . . . . . . . . . . . . . . 42

1. The Pe Peri riodic odic Table Table and Electro Electron n Confi Configu gura rati tion on . . . . . . 42 1. WHY CHEMIST CHEMISTRY? RY? . . . . . . . . . . . . . . . . . . . . . . . . 9

Reading : Dmitri Ivanovich

1. 1. What is Science?. . . . . . . . . . . . . . . . . . . . . 12

Mendeleev (1834-1907) . . . . . . . . . . . . . . . . . . . .43

Reading : A : A Short History of Chemistry . . . . . . . 14

1. 1. Groups Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

1. 2. The Experimental Experimental World World Of Chemistry Chemistry . . . . 16

1. 2. Electron Electron Confi Configu gura rati tion on . . . . . . . . . . . . . . . .45

1. 2. 1. Chemistry is an Experimental Science. . 6

1. 3. Finding Finding Group Group and Peri Period od Numbe Numbers rs . . . . .48 .48 2. The peri periodic odic Trends Trends . . . . . . . . . . . . . . . . . . . . . . .51

2. MATTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2. 1. Atomic Atomic Radi Radius us . . . . . . . . . . . . . . . . . . . . . . .51

2. 1. States States Of Matter Matter . . . . . . . . . . . . . . . . . . . . . 21 2. 2. Ionic Ionic Radi Radius us . . . . . . . . . . . . . . . . . . . . . . . .53 2. 1. 1. Solid State. . . . . . . . . . . . . . . . . . . . . . . 22 2. 1. 2 Liquid State . . . . . . . . . . . . . . . . . . . . . . 22 2. 1. 3. Gaseous State. . . . . . . . . . . . . . . . . . . . 22 2. 2. Classifica Classification tion Of Matte Matterr . . . . . . . . . . . . . . . 24 2. 2. 1. Pure Substances. . . . . . . . . . . . . . . . . . 24 2. 2. 2. Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . 27 3. ATOM ATOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2. 3. Electronegativity . . . . . . . . . . . . . . . . . . . . .53 2. 4. Metal tallic lic and Nonme Nonmetal tallic lic Proper Properti ties es . . . . .5 .55 5 2. 5. Ioni Ioniza zati tion on Energy Energy . . . . . . . . . . . . . . . . . . . .56 .56 3. The Rections Rections Of Alkali Alkali Metals Metals . . . . . . . . . . . . . .60 4. The Rections Of Alkaline Earth . . . . . . . . . . . . . .62 5. Chlorine Chlorine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65

3. 1. Structure Of Atom . . . . . . . . . . . . . . . . . . . . 29

5. 1. Occu Occurren rrence ce . . . . . . . . . . . . . . . . . . . . . . . . .65

3. 2. Subatomic Particles Particles . . . . . . . . . . . . . . . . . . 30

5. 2. Chem Chemical ical Propert Properties ies . . . . . . . . . . . . . . . . .65

3. 3. The Atomic Terminology Terminology.. . . . . . . . . . . . . . . 33

Supplementary Questions . . . . . . . . . . . . . . . . . .67 Multiple Choice Question . . . . . . . . . . . . . . . . . .68

3. 3. 1. Atomic Number (Z) . . . . . . . . . . . . . . . . 33 3. 3. 2. Atomic Mass Number (A) . . . . . . . . . . . 33 3. 3. 3. Isotopes. . . . . . . . . . . . . . . . . . . .. . . . . 35 3. 3. 4. Ions. . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 3. 3. 3. Average Atomic Mass . . . . . . . . . . . . . . 37

Chapter 3

Chemical Bonds INTRODU INTR ODUCTIO CTION N . . . . . . . . . . . . . . . . . . . . . 72

Supplementary Questions . . . . . . . . . . . . . . . . . 38 Multiple Choice Questions . . . . . . . . . . . . . . . . . 39

1. CHEMICAL BONDS AND THEIR FORMATI FORM ATIONS ONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Reading: How to Write Lewis Structures

1. 2. Heat Change in the

Of Molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

1. 3. Conductivity of Solutions . . . . . . . . . . . . . 112

1. 1 Ionic Bond . . . . . . . . . . . . . . . . . . . . . . . . . . 76

1. 4 Change in Freezing and Boiling Points . . 114

1. 1. 1. Sodium chloride . . . . . . . . . . . . . . . . . . 79

1. 5 Dilute and Concentrated Solutions. . . . . . 115

1. 2 Covalent Bond . . . . . . . . . . . . . . . . . . . . . . . 81

Dıssolutıln

. . . . . . . . 111

Reading: Water: The Basis of Life . . . . . . . . . . . . 117

1. 3. Coordinate Covalent Bond. . . . . . . . . . . . . 84

2. SOLUBILITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

2. SOME INTERMOLECULAR FORCES . . . . . . . . . 88

2. 1. Factors Affecting Solubility . . . . . . . . . . . 120

2. 1. Dipole Dipole Force . . . . . . . . . . . . . . . . . . 88 2. 2. Van Der Waals Forces. . . . . . . . . . . . . . . . . 88 2. 3. Hydrogen Bond . . . . . . . . . . . . . . . . . . . . . . 89

Reading: How Does an Iron Work? . . . . . . . . . . . 91 Periodic Table . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

Raeading : Water: The Bends . . . . . . . . . . . . . . 121 3. MIXING AQUEOUS SOLUTIONS. . . . . . . . . . . . 125 3. HYDROLYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Supplementary Questions . . . . . . . . . . . . . . . . 131 Multiple Choice Questions . . . . . . . . . . . . . . . . 133

Supplementary Questions. . . . . . . . . . . . . . . . . . 94 Multiple Choice Questions . . . . . . . . . . . . . . . . . 95 Chapter 6 Chapter 4

Gases INTRODUCTION . . . . . . . . . . . . . . . . . . . . . 98

1. THE PRESSURE OF A GAS. . . . . . . . . . . . . . . . . 98 2. THE IDEAL GAS LAW . . . . . . . . . . . . . . . . . . . . . 98 3. DENSITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Reading : A Gas MIxture : Air . . . . . . . . . . . . . . 101 Supplementary Questions. . . . . . . . . . . . . . . . . 102

Measuring Concentration INTRODUCTION . . . . . . . . . . . . . . . . . . . . 136

1. PERCENTAGE CONCENTRATION . . . . . . . . .137 1. 1 Mass Percent . . . . . . . . . . . . . . . . . . . . . . . 137 1. 2 Volume Percent . . . . . . . . . . . . . . . . . . . . . 141 2. MOLARITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 2. 1. The Preparation of a solution with a desired concentration . . . . . . . . . . 146

Analysis of Some Ions . . . . . . . . . . . . . . . . . . . . 150 Supplementary Questions . . . . . . . . . . . . . . . . 151 Multiple Choice Questions . . . . . . . . . . . . . . . . 153

Chapter 5

Solutions INTRODUCTION . . . . . . . . . . . . . . . . . . . . 104

Chapter 7

1. NATURE OF SOLUTIONS . . . . . . . . . . . . . . . . . 105 1. 1. The dissolution Process. . . . . . . . . . . . . . 109

Chemical Equilibrium INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . .156

1. Physical Equilibrium . . . . . . . . . . . . . . . . . . . . .156

5. NEUTRALIZATION REACTION . . . . . . . . . . . . . 186

2. Chemical Equilibrium . . . . . . . . . . . . . . . . . . . . 157

6. TITRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

3. Factors Causing Equilibrium . . . . . . . . . . . . . . 158

Supplementary Questions. . . . . . . . . . . . . . . . . 190

3. 1. Tendency Toward Minimum Energy . . . . 158

Multiple Choice Questions . . . . . . . . . . . . . . . . 191

3. 2. Tendency Toward Maximum Randomness . . . . . . . . . . . . . . 158 4. THE EQUILIBRIUM CONSTANT EXPRESSION . . . . . . . . . . . . . . . . 160 5. FACTORS AFFECTING EQUILIBRIUM. . . . . . . 163

Chapter 9

Process of Redox

5. 1. Effect of concentration. . . . . . . . . . . . . . . 163 5. 2. Effect of Pressure and Volume . . . . . . . . 166 5. 3. Effect of Temperature. . . . . . . . . . . . . . . . 167 5. 4. Effect of Catalyst . . . . . . . . . . . . . . . . . . . 168

INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . 194 1. OXIDATION – REDUCTION REACTIONS . . . . . 194 1. 1 Oxidation State. . . . . . . . . . . . . . . . . . . . . . 195

Reading: Haber Process . . . . . . . . . . . . . . . . . . 169 Supplementary Questions . . . . . . . . . . . . . . . . . 170 Multiple Choice Questions. . . . . . . . . . . . . . . . . 172

1. 2 Oxidation - Reduction Half – Reactions . . . . . . . . . . . . . . . . . . . . . . . . 197 1. 3. Balacing Oxidation –

Chapter 8

Reduction Reactions. . . . . . . . . . . . . . . 198

Acids and Bases INTRODUCTION . . . . . . . . . . . . . . . . . . . . . 72

2. ELECTROCHEMICAL CELLS . . . . . . . . . . . . . 203 2. 1. Standard Electrode Potential . . . . . . . . . 205

1. ACID – BASE THEORY . . . . . . . . . . . . . . . . . . . 174 3. CORROSION. . . . . . . . . . . . . . . . . . . . . . . . . . . 208 1. 1 Arrhenius Acid – Base Theory. . . . . . . . . . 174 1. 2 Bronsted – Lowry Acid – Base Theory . . . . . . . . . . . . . . . . . . . . . 175 1. 3. General Properties of Acids . . . . . . . . . . . 176 1. 4. General Properties of Bases . . . . . . . . . . 176 2. IONIZATION OF WATER . . . . . . . . . . . . . . . . . . 177 3. PH SCALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 4. STRENGTH OF ACIDS AND BASES . . . . . . . . . 181 4. 1 Acid Strength . . . . . . . . . . . . . . . . . . . . . . .181

4. BATTERIES (VOLTAIC CELLS) . . . . . . . . . . . . 210 5. ELECTROLYSIS AND ELECTROLYTIC CELLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 5. 1 ElectrolysIs of Water . . . . . . . . . . . . . . . . . 213 5. 2 Electrolysis of Molten Nacl . . . . . . . . . . . . 214 5. 3. Purification of Metals And Electroplating . . . . . . . . . . . . . . . . . . . . . 215

Supplementary Questions . . . . . . . . . . . . . . . . 219 Multiple Choice Questions . . . . . . . . . . . . . . . . 221

4. 2 Base Strength . . . . . . . . . . . . . . . . . . . . . . .182

Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

4. 3. Relationship Between K a And K b . . . . . . .185

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

INTRODUCTION Chemistry simply can be defined as the study of matter and its changes. This definition shows that the science of chemistry encompasses all substances in our life! In fact, chemistry is life! In this chapter, we try to explain why chemistry is so important in our lives. At the end, you’ll see why chemistry is life. Chemistry is a branch of natural sciences, such as physics, biology and geography. As we hear the word science, we should remember that it is the collective knowledge accumulated throughout the world’s history. Although it’s a branch of the natural sciences, chemistry is unique!

Tree of natural sciences

Chemistry is unlike any other natural sciences because of one crucial difference; only chemistry is interrelated with all of the others. In other words, chemistry is related with all substances and objects. Chemistry is in everything! When we think about it, we can easily realize that there is nothing existing in our world that is not related to chemistry. 8

CHEMISTRY Ninth Grade

Chemistry is closely interweaved with all of the sciences.

1.1.

WHY CHEMISTRY?

Because, chemists always synthesize or discover new substances and help

technological developments. The modern residence you live in, the car your parents drive, the TV you watch, the Playstation you enjoy are all examples of the wonders achieved through the use of chemistry. Because, chemists produce all modern or traditional herbal drugs and medicine;

analyze blood, hormones, and urine; as well as diagnoze illnesses. This can only be possible through the use of chemistry. Because, potable purified water, all organic or GM (Genetically Modified) fruits

and vegetables are works of chemists. Because, if we look around us, chemistry is everywhere. The water you drink,

the air you breathe, the bread you eat, the CD you listen to or the clothes you wear, are all made out of chemicals! Now, you see why chemistry is all around us. Introduct�on to Chem�stry

9

CHEMISTRY IS LIFE

All toys, including dolls and models, can be produced with the knowledge of chemistry.

We can decorate, paint, protect and clean our houses thanks to chemistry.

This reading simply explains the importance of chemistry in our lives. You can see chemistry in every part of our life. For example, while preparing this textbook we used pencils, pens and papers. To type it, computers were used and printers to print its pages with different inks (paints); paper and printing machines were also utilized. All materials and machines used in the New polymers are making our life easier.

printing of this book are also the products of chemicals. In other words, they are produced with the help of different elements or/and compounds. All these are the subjects of chemistry. Yet another example, what if you were to become ill, how would your ailment be diagnozed?

Computer technology only thrives with the help of chemistry.

Long-term preservation of our packaged food is only made possible with chemicals. Chemistry even helps us with our clothing and footwear.

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Without chemicals, our body, for example, and our nervous system couldn’t function.

Chemistry helps us in coloring our world.

Doctors may guess the disfunction (illness) you are suffering from. In other words, the apparent chemical change that occured in your organs (in the tissues or cells). If a doctor diagnoses your illness, he will probably advice some medicine (products of chemicals) or different remedies (all contain different compounds or chemicals).

No chemistry! No transportation!

You cannot escape from the scope of chemistry because we are living in a material world, or chemical world. Have you ever thought that we need chemicals everyday in every second to live? In fact, the air we breathe contains N2, O2, . . . all are chemicals. The water we drink many times a day is also a chemical. Salt, pepper, sugar, ice-cream, all fruits and all vegetables (all foods) are all composed of chemicals!

All the drugs are produced from chemicals.

Paper and pencils are all produced with chemical materials.

All patients need the products of chemistry in diagnoses or treatments.

Introduction to Chemistry

11

1. 1. WHAT IS SCIENCE? As you remember, chemistry is a branch of science. To understand this better,

Science The word science comes from the Latin “scientia” which means know ledge.

let’s first see what science is. People observe their surroundings, other creatures and themselves to discover their nature and to find out their relationship among themselves. When they come face - to - face with problems, they use systematic methods to overcome the m. From ancient times until today, acquired knowledge has been collected on a regular basis. This accumulated knowledge is known simply as science. Throughout the world’s history, humankind’s knowledge has been continuously transmitted to newer generations. People shared this knowledge by writing, speaking and searching for the relations between the cause and effect of facts. As a result, we were able to reach conclusions. All of these activities, hypothethized carefully and tested systematically, are called scientific studies. Individuals who conduct scientific studies are called scientists.

Chemist : A scientist who studies chemistry.

Chemists are scientists.

Classification of Sciences Natural Sciences Chemistry Biology Physics Earth Sciences Life sciences Astronomy . . .

Social Sciences Sociology Philosophy Psychology Divine Sciences Politics . . .

Science disciplines can also be classified in different ways: such as physical sciences, pure and applied sciences, social sciences, positive sciences, life sciences, etc... 12


Today’s generation is grateful for past and present scientific studies since their welfare has been enhanced. Chemistry, as we’ve seen, is an important branch of science. It’s certainly true that chemists who study the changes that occur in the structure of substances have a great contribution in the development of science and technology. The applications of scientific principles in the service of mankind is called technology . Although developments in industry and technology enhance the welfare of human beings, there are negative sides of scientific developments. Some gases cause air pollution, poisonous chemical wastes and their by-products cause cancer; all weapons and atomic bombs threaten the balance of mankind. At first glance, the branches of scientific studies seem to be boring due to groups of formulas, theories and definitions. But, actually, science reflects the attractive sides of the universe and informs us what is happening in our their surroundings.

Steps of Scientific Study All scientific studies should be carried out in certain steps. 1. Observation

Observation, which is the first step of scientific study, is the collection of information gathered from the use of our senses. A subject can be observed through touch, taste, hearing, or smell. During observations, better results can be obtained by using instruments that increase the sensitivity of our senses. We must always keep in mind that the observation process is not right or wrong. 2. Hypothesis and (Research for Reasons of Regularities)

Hypothesis is the explanation of an occurence or a problem by using the knowledge obtained from previous observations. All hypotheses may not always be true. For this reason, the following steps should be applied one by one to prove a hypothesis. 3. Experiment

The collection of actions and observations performed to verify or falsify a hypothesis or research. Experiments are generally performed in laboratories. 4. Sharing Results

An observation in a lake

The definition of science, as we mentioned before, is the accumulated knowledge that has been formed through centuries. If we share that knowledge with others, we cannot continuously start from the beginning of our scientific studies. Today, telecommunication technologies have changed the world into a global village; hence, news can now be spread throughout the world in a matter of seconds through the use of the Internet. Similarly, scientific and technological development can easily be propagated through the means of books, scientific journals and the Internet. In a science class

Computer technologies have changed the world into a global village. Introduction to Chemistry

13

A SHORT HISTORY OF CHEMISTRY

The word chemistry officially comes from the old French alkemia , but has an even older root stemming from the Arabic origin of al-kimia , which means the art of transformation. We can trace the beginning of chemistry to ancient times. The first chemists were mainly concerned with pottery, metallurgy, dyes, and food. We can retrace the earliest chemical principle to 3500 B.C. in Egypt and Mesopotamia.



Chemistry’s beginning, or alchemy, as it was then known, was equal to performing 



magic or having superpowers. Alchemy was the practice of combining elements

 





medicine. 



of chemistry, physics, religion, mysticism, astrology, art, signs, metallurgy, and

The most famous interests of alchemists were the transmutation of metals to gold, and the search for Ab-u hayat , or the elixir of life to produce immortality.



Greek thinkers believed that there were just four states of matter; water, fire, earth, and air (in some sources, the fifth was the cosmos).

In the Middle Ages, Muslim scientists Jabir bin Hayyan - the first to use lab equipment - was known as Geber, or the Father of Chemistry in Europe; and Abu Bakr-Al-Razi (865-925); both greatly contributed in chemistry’s early beginnings.

Jabir bin Hayyan (721 - 815) He is known as the Father of Chemistry. 14


Latin translations of these two Muslim scientists’ discoveries helped build the fundamentals of chemistry. Six centuries later, European scientists Robert Boyle and Antoine Lavoisier - regarded as the Fathers of Modern Chemistry - built the basis for what we know today as modern chemistry

R. Boyle (1627-1691)

A. Lavoisier (1743-1794)

The last 200 years have heralded a multitude of scientific equipment and millions

Of all the sciences, did you know that

of chemical compounds which were all discovered through synthesis.

chemistry has the largest encyclopaedia of terminology?

Even laboratories have been altered dramatically through history.

In the 21 st century, chemistry has become the largest collection of knowledge (science) because of its many sub - branches. Today, the world’s largest and most

CAS = Chemical Abstracts Service

current database that contains information regarding chemical substances, CAS, has more than 29 million chemical substances. Everyday, 4000 new substances are added to this database. Introduction to Chemistry

15

1. 2. THE EXPERIMENTAL WORLD OF CHEMISTRY The word experiment comes from Latin experiri or experimentum, which means attempt. In the scientific method, experiments are the processes from which all empirical knowledge is born.

1. 2. 1. CHEMISTRY IS AN EXPERIMENTAL SCIENCE In chemistry, chemists always need experiments to research cause/effect relationships between phenomena. Like other scientists, such as physicists, biologists, and many others, chemists must follow four systematic steps while experimenting:

1. Setting up the experimental equipment and procedures 2. Conducting the experiment 3. Recording data 4. Analyzing results, reaching a conclusion and sharing results Through the use of experiments, chemists understand the properties and changes which occur in matter and the various reactions between different substances.

1. 2. 2. WORKING IN A CHEMISTRY LABORATORY Experiments should be performed in laboratories. A laboratory, often simply

Lab. = Laboratory

called a lab, is a specially designed environment to conduct experiments or scientific research. While performing chemistry experiments in school labs, chemicals, water, fire, and glassware should be handled carefully. Although laboratories are not playgrounds, they can be very enjoyable places. But, safety always comes first; sometimes small unexpected accidents may cause serious injuries. Therefore, students, teachers, and lab technicians should always use utmost caution in a lab environment.

Ensuring A Safe Laboratory In a chemistry lab, these must be available:

16


a. Fire extinguisher

b. Fire blanket

c. Safety shower

d. Eyewash station

e. First aid kit

f. Container for sharp objects

g. Air conditioner

h. Telephone

To ensure that your school lab is a safe place, here are some basic safety rules about laboratory equipment and hazard warning symbols. Safety Rules Students must always obey the following safety rules in a school lab: 1. Always listen carefully to all instructions given by your chemistry teacher or lab technician before any experiment. 2.

Learn all the safety rules necessary for your experiment.

3. Always wear a lab jacket (apron) and safety goggles (glasses). 4.

Read all necessary information about the experiments.

5. Wear gloves when using heat, chemicals and glassware in experiments. 6.

Do not throw any chemicals.

7.

Do not touch chemicals with your fingers.

8.

Tie long hair.

9.

Do not horse around in a lab.

10. Quickly report all accidents to your teacher. 11. Do not eat, drink, smell or taste any chemical.

Safety always comes first in a lab Introduction to Chemistry

17

Laboratory Equipment In chemistry experiments, different lab equipment can be used. Some of them appear below:

Do not use any lab equipment without permission! Test Tube (Mixing substances)

Erlenmeyer flask (Toxic substances)

Beaker (Used for measuring approximate volumes)

Test tube holder (To hold hot test tubes)

Graduated cylinder (To measure exact volumes of liquids)

Stands and clamps (To hold and fix lab equipment)

Wash bottle (Dilution)

Burners (For heating purposes)

Round bottom flask (Mixing, collecting liquids)

Funnel (Used for filtration or pouring liquids)

Test tube rack (To park test tubes)

Tripod (Used with burners)

Some equipment may cause fatal accidents!

18


Hazard Warning Symbols Many chemicals are hazardous. Therefore, hazard warning symbols are placed on containers of harmful chemicals and on laboratory walls to explain and inform of possible dangers.

 Explosive

Toxic

Harmful

Oxidizing

HAZARD Corrosive

Eye Protection

 Irritant

Radioactive

Shock

Flammable

Hazard labels or warning symbols can be found in a lab, but they also can be seen in many other venues in life, such as on r oadsides...


19

2. MATTER In chemistry, matter is simply everything; every physical body or substance. Matter has mass and o ccupies volume. Matter = Substance(s)

If you remember, we defined chemistry as the study of matter and its changes in the previous chapter. Look at the picture given below, the mountains, rocks, trees, and lakes pictured are all composed of thousands of substances.

In the physical world, everything can be accepted as matter.

2. 1. STATES OF MATTER In this chapter we will stud y the states of matter, its classification and properties. In addition to these, we will see how different substances can be separated. In daily life, we frequently ask, “what is the matter?” or “what is the matter with you?”. Here, matter means how you are doing or what’s going on with you.

20


Matter can be found in different states, or phases, in the universe. The most common states are: solid, liquid and gaseous. Plasma is often called the fourth state of matter.





 

A plasma TV became popular during the last decade.

Liquid

Gas

Sea water

Solid

Air

Sand

States of matter

Through heating and cooling (or changing pressure), matter may alter from one state to another, (names and directions of these changes are given) as follows:

Gaseous (adjective) Gas (noun)



                    

 

      

     

  




21

2. 1. 1. SOLID STATE Solid substances have a definite volume and shape. The particles (atoms or molecules) in solids are very close to each other - there is a minute amount of space between atoms or molecules. Solids can be picked up and carried around without a special container.

All pencils and their containers are solid and have a certain shape.

Various solids have different shapes.

2. 1. 2. LIQUID STATE Liquids have definite volume, but no d efinite shape. Liquids can flow, be poured, and take the shape of their container. The particles in liquids are more loosely contained than those of solids. Hence, that’s how liquids can flow.

Liquids take the shape of their containers.

Different liquids

2. 1. 3. GASEOUS STATE Gases have no definite volume and n o definite shape. A gas takes the shape and fills the volume of any container in which it is placed. Gas particles are apart from each other so they can move freely.

Although many gases are colorless, some of them are tinted. For example,

Gases will spread out if they are not in a container. Most gases are colorless, and, therefore, cannot be seen.

nitrogen dioxide ( NO 2) has a reddish brown color and is an extremely toxic gas!

We all live in a gaseous world. 22


P l a s m a and O u r Lightning

L i v e s

P lasma

Aurora

has no definite volume or shape and contains electrically charged particles. Plasmas are collections of freely moving particles. Plasma temperatures may change, but they are generally very hot (a few thousands to millions of degrees °C). Fluorescent light and high - intensity arc lamps are some examples of where plasma can be seen. In addition to these, many products today are manufactured using plasma technologies. Computer chips, aircraft parts, systems for safe drinking water, high efficiency lighting products are all examples of these technologies. The word P l a s m a entered our dictionaries in 1929.

Stars in galaxies

Flame


23

2. 2. CLASSIFICATION OF MATTER Matter exists in millions of different forms in the world. Water is matter just like Particles in elements and compounds cannot be seen with the naked eye.

gold. As ice-cream is composed of different states, so is the sun. Matter can be easily classified according to its purity, as follows:

2. 2. 1. PURE SUBSTANCES Tap water (city water) is not a pure substance because it not only contains

Pure substances are elements and compounds. They have only one type of

water molecules, but also particles. Tap

particle in their structure. For example, pure water only contains water

water contains other ions, such as

molecules, and gold solely gold atoms.

calcium, which causes hardness of water.

Gold

Pure Water

Aluminum is an element.

A gold atom (particle)

A water molecule (particle)

NaCI is a compound. Examples of pure substances 24


Elements Elements contain only one type o f particle (the atom). All elements are shown by



the use of symbols; gold (Au), oxygen (O) and calcium (Ca) are some examples of elements. Today, 116 elements are known; 92 of which are called natural elements. Elements can be classified as metals and nonmetals.





All symbols for elements are placed on a special table called the periodic table.

He, Ne, Ar, Kr, Xe, and Rn are named Noble gases.These are unreactive and very stable elements (Table 1).

The symbols for elements can have up to two letters in Latin. The first letter is always capitalized and the second must be lower - cased. For example, H : Hydrogen and Al : Aluminum Table 1: The Periodic Table of Elements is the most popular table in chemistry

(If element is unnamed then three letters

such

as

Uub,

Uuq

etc.

temporarily are used in symbols).

Properties of elements. 1. An element cannot be broken down into another substance. 2. The basic building blocks of elements are atoms. 3. When elements react with each other, they produce compounds.

u m i n

,

A l

C o p

p e

r ,

u m A l

n , Z

L

e

a d ,

C u

P b

Z

c i n

I o d i

n e , I

Metals

S u l f u

r , S

Nonmetals

1. They are good conductors of electricity.

1. They do not conduct electricity, except for carbon (graphite).

2. They are solid at room conditions.

2. They can be solid, liquid or gaseous at room conditions.

3. They have a metallic, shiny color.

3. They have a dull color.

4. They can be hammered into sheets.

4. They are brittle (cannot be hammered).

5. They can be drawn into wires.

5. They cannot be drawn into wires. Introduction to Chemistry

25

Compounds Salts, acids, bases, and oxides are all different classes of compounds. Unlike the elements that only amount to 116, there are millions of compounds in the world. About

29,000,000

compounds

are

All compounds are shown by formulas. For example, H2O for pure water and CO2 for carbondioxide. All compounds contain at least two types of particles

known.

(atoms).

Copper (II) chloride (Green / Blue) Cobalt (II) chloride (Red / Pink)

Properties of Compounds 1. A compound can be decomposed into components through chemical methods. 2. Elements combine in definite proportions by mass to form compounds. 3. The chemical properties of compounds are different from those of elements Copper (II) oxide(Black)

found in that compound. Ammonium dichromate (Orange)

Compounds must be kept in closed containers. 26


2. 2. 2. MIXTURES Mixtures are combinations of two or more pure substances. In mixtures, the chemical properties of the starting substances do not change. Mixtures can be homogeneous or heteregeneous. In a homogeneous mixture, the composition of its parts are equal. But in heteregeneous mixtures, the composition of its

homogeneous = same type heter o g eneou s = different type

parts is different.

sulfur

water

sand

A heterogeneous mixture (sand + water + sulfur)

Properties of Mixtures 1. Components of a mixture have their respective chemical properties. 2. Mixtures may be composed of different elements and compounds. 3. There is no fixed ratio among the components. 4. Components can be easily separated by physical means.

copper (II) sulfate + water

water sugar carbondioxide caramel phosphoric acid coke aroma caffeine etc.

Fizzy drinks are also mixtures.

A homogeneous mixture

Unlike compounds, mixtures can be separated into their parts (components) by using physical methods.

Types of mixtures according to physical states Heteregeneous Mixtures

Homogeneous Mixtures (Solutions) State ________

Examples __________________

State ________

Examples _____________

Solid

Coins, dental f illings

Solid

Liquid

Fizzy drinks

Liquid

Milk

Air

Gas

Aerosols

Gas

Homogeneous

mixtures

are

called

SOLUTIONS.

Mineral ores


27

3. ATOM For ages, humankind has been interested about the structure of substances. For centuries, thinkers, philosophers, alchemists, and scientists have all tried to discover the most fundamental unit of matter. How is matter made up? What are its fundamental substances? How are its structures? In the past, the answers to these questions were not easy to formulate. Let’s try a simple exercise in order to better understand just how hard this must have been: Take a square piece of paper with dimensions of 5 cm . 5 cm. First, tear the paper in half, then take one of the halves and tear again. Continue this process up to 10 times (Figure 1). Hopefully, you were able to do so.

Figure 1: How small the atom is!

If you do this 50 times, how small will that piece of paper become (probably you cannot achieve this)? How can you call this smallest part of paper? For the last 200 years, scientists have accepted that the smallest parts of substances are called atoms. An atom is a world, according to some scientist, and it works with a mechanism that is not completely understood. But this much is known, an atom has basically two parts: A nucleus (central part) and electrons (very fast moving particles) around this center.

STM Q. Is it possible to see an atom? A. No. But, Scanning Tunneling Microscope (STM) gives us the chance to study and view individual atoms on the surface of materials. STM was invented in 1981 by Gerd Binnig and Heinrich Rohrer in Switzerland. These scientists won the Nobel Prize in Physics (1986). A STM 28


3. 1. STRUCTURE OF ATOM Atom is a term that originates from the Greek word atomos, which means indivisible. Atoms are accepted as indivisible because of their minute size. When we discuss atomic size, we use nanometers (0.000000001m scale). For example,

1 nanometer (nm) = One billionth of a meter

the diameter of an atom ranges from about 0.1 to 0.5 nanometer (Figure 2).



           



Nanotechnology is the design, study

and

control

of

matter

using

the

nanometer scale. This word was first used (defined) in 1974 by Japanese scientist Prof. Norio Taniguchi at Tokyo Science University. Figure 2: Atomic diameter ranges from about 0.1 to 0.5 nm.

An atom is made up of two main parts, the nucleus and electrons. 





History of The Atom It’s impossible to weigh or isolate a single atom. We know that the atom is so tiny that we cannot feel it by using our senses. Therefore, the development of atomic theories have been based on indirect methods. At the beginning of the 19 th century, the existence of atoms had been a point of contention. Erstwhile, Muslim scientist Jabir Bin Hayyan (721-815) had discovered that an individual atom could be split to release a huge amount of energy. John Dalton (1766-1844) presented the first scientific proof of the existence of the atom based upon his experimental study. At the start of the 20 th century, the theories and empirical studies conducted by Thomson, Rutherford, Planck, Einstein, Bohr, Shrodinger... that delved into atom’s structure greatly impacted today’s progress.

Computer image of chromium on iron atoms.


29

3. 2. SUBATOMIC PARTICLES Up to the 20th century, atoms were accepted as indivisible (it cannot be divided into small parts). Today, we know otherwise. Atomic radius of the hydrogen (H) atom is 37 picometer (37 . 10–12m)!

During the last century, nuclear reactions showed us how an atom’s division is possible. With the help of nuclear reactions, an atom’s nucleus can be divided into parts to produce huge amounts of energy. Now let’s answer the next question: What are the subatomic particles of an atom? The shape of an atom is assumed to be a simple sphere, but it actually might be an empty sphere (Figure 3).

   

    

Figure 3: A representation of an atom

In chemistry, the term nucleus (plural

In an atom sphere, there is a nucleus at the center. An atom’s nucleus contains

nuclei) is used for atoms as it is used for

protons and neutrons. Electrons are also found in an atom, but they move so

the nucleus of a cell in biology.

quickly that we only know that they are around the nucleus but not exactly where?! 









Proton (p) : Positively charged particles found in the nucleus of an atom. Neutron (n) : Uncharged particles found in the nucleus of an atom. Electron (e – ) : Negatively charged particles found around the nucleus of an atom (Table 2). 30


Symbol

Charge

amu

Charge(C)

Mass(kg)

Amu : atomic mass unit

1 amu means 1/12 of the mass of a

Proton

p

+1

1

1.6 .

Neutron

n

0

1

1.6 . 10–19 1.67 . 10–27

Electron

e

–1

~ 1/2000

10–19

1.67 .

10–27

carbon - 12 nucleus. 1 Coulomb ( C ) : Amount of electrical charge carried by a current of 1 ampere

0

9.11 . 10–31

(A) in 1 second.

Table 2: Subatomic Particles

Although an atom was once known as the smallest particle, today we know that even smaller particles exist in an atom (Figure 4).

Inside the atom In the 20th century, we have learned that there are subatomic particles in the atom, such as the proton, neutron and electrons. But today, scientists relate to the atoms’ subparticles such as quarks, leptons, neutrinos, muons, photons, mezons, etc...

Figure 4: Particle world of the atom


31

The lightest basic particle

of an atom, which has a mass of approximately

1/2000 amu, is the electron. For the neutral atom, the number of protons and electrons are equal. Electrons rotate at a great speed at specific, fixed energy levels (shells) around the nucleus. The first shell is th e nearest to the nucleus, and is called the “K” shell. The second shell is known as “L”, the third is “M” ... etc. Each shell has a certain capacity of electrons, and this capacity is defined by the equation of 2n 2. Here, n shows the number of shells. If an atom only has one shell, it can have up to 2 electrons. An atom’s electrons in its outermost shell are called valence electrons. Thus, the first energy le vel (K) can occupy a ma ximum of 2 electrons, the second energy le vel (L) can ha ve a ma ximum capacity of 8 electrons, and so on. The ma ximum number of electrons found in each shell can be summarized as such:

First shell (K)

for n = 1

⇒

2

·

n2 = 2

·

12 = 2e–

Second shell (L)

for n = 2

⇒

2

·

n2 = 2

·

22 = 8e–

Third shell (M)

for n = 3

⇒

2

·

n2 = 2

·

32 = 18e–

Fourth shell (N)

for n = 4

⇒

2

·

n2 = 2

·

42 = 32e–

Fifth shell (O)

for n = 5

⇒

2

·

n2 = 2

·

52 = 50e–

Configuration of electrons in their shell.

1 Show the electron configuration for the following elements and indicate their number of energy levels. a. H : 1 electron

b. O : 8 electrons

c. Mg : 12 electrons

d. Ca : 20 electrons

a. H : 1)

Hydrogen has only one energy level.

b. O : 2) 6)

Oxygen has two energy levels.

c. Mg : 2) 8) 2)

Magnesium has three energy levels.

d. Ca : 2) 8) 8) 2)

Calcium has four energy levels.

Exercise 1: Find the number of valence electrons in, a. Lithium - 3 electrons 32


b. Aluminum - 13 electrons

3. 3. THE ATOMIC TERMINOLOGY

There are some basic terms about the atom in chemistry. In order to study the calculations of the atom, these terms should be understood. 3. 3. 1. ATOMIC NUMBER (Z)

The number of protons in an atom is called atomic number and is represented by Z . Atomic number = Number of protons Each type of atom posesses a different atomic number that specifies its amount of protons. For example, a calcium atom has 20 protons; its atomic number

Each car has a different licence plate number

is 20. For a neutral atom,

the atomic number, the number of protons and the number

of electrons are equal. Atomic number = Number of protons = Number of electrons Z = p = e– 3. 3. 2.

ATOMIC MASS NUMBER (A)

An atom’s total number of protons and neutrons is called its atomic number

mass

and denoted by A. An atom’s mass is found in its nucleus and can be

The atomic mass number can sometimes be called nucleon number.

calculated as follows: Atomic Mass Number = Number of protons + Number of neutrons A = p + n

2

What is the atomic mass number of molibdenum, which has 42 protons and 54 neutrons?

96

M o

54 42

By using the following formula, molibdenum’s atomic mass number can easily be calculated. A = p + n A = 42 + 54

⇒

A = 96

M o l i b d e n u m

Molibdenum is a metal with a mp of 2610 °C and bp of 5560 °C

Exercise 2:

Calculate the number of neutrons in selenium, (Se) which has 34 protons and an atomic mass number of 79. Introduct�on to Chem�stry

33

X Representation

q = p – e– A = p + n

The X representation details an atom’s number of electrons, number of protons, number of neutrons, charge and atomic mass number. Here, X represents any symbol of an element such as Al, K, Mg etc... Now, let’s see an example. A neutral sodium atom (Na) has 11 protons, 11 electrons, 12 neutrons, and an atomic mass number of 23, which are shown thusly: A = 23

0

n = 12

Na

e– = 11

p = 11

3 What is the number of neutrons and the charge of a bromine ion? 80 ? 35

Bromine is a very toxic and corrosive liquid. 34

CHEMISTRY N�nth Grade

?

Br

36

If A = p + n

⇒

n = A – p and n = 80 – 35 = 45

If q = p – e –

⇒

and then q = 35 – 36 = –1

3. 3. 3.

ISOTOPES

All of the atoms’ nuclei of an element have the same number of protons, but their number of neutrons may be different. For example, there are three types of hydrogen atoms (Figure 5), and they differ only in their number of neutrons.

Figure 5: Types of hydrogen atoms

Isotopes can be defined as atoms that have the same number of protons but a

different number of neutrons (Table 3).

Isotopes are similar to human beings in the world.

Since the number of p rotons and electrons of an isotope are equal, isotopes have similar chemical properties but different physical properties.

Element

Hydrogen

Atomic number

Number of neutrons

Atomic mass number Symbol

1

–

1

1H

99.985

1

1

2

2H

0.015

1

2

3

3H

3

3

6

6Li

7.52

3

4

7

7Li

92.48

6

6

12

12C

98.89

6

7

13

13C

1.11

8

8

16

16O

99.76

8

9

17

17O

0.04

8

10

18

18O

0.20

17

18

35

35Cl

75.4

17

20

37

37Cl

24.6

example,

69.1 30.9

35 18 17

Lithium

Carbon

Oxygen

Chlorine

Copper

Uranium

Natural abundance (%)

very small

29

34

63

63Cu

29

36

65

65Cu

235

235U

0.71

238

238U

99.28

92 92

143 146

Isotones

Atoms having the same number of neutrons but different number of protons

36 18 18

are

called

isotones .

For

Cl, Chlorine isotones

Ar, Argon

Table 3: The natural abundance of some isotopes Introduct�on to Chem�stry

35

3. 3. 4. IONS

Atoms of an element are neutral particles. Their number of protons and electrons are equal. Therefore, the charge of a neutral atom is zero. Otherwise, the atom is charged. Charged atoms are simply called are two types of ions: cations and anions.

ions.

There

If the number of protons is greater than the number of electrons in an atom, it is called a cation. Or, if the number of protons is smaller than the number of electrons in an atom, it is called an anion. The charge of an atom can be determined by the following equation q = p – e – here, Positively charged atoms = CATION

p : is the number of protons

Negatively charged atoms = ANION

e– : is the number of electrons q : is the charge of an atom Now let’s see some examples of sodium and oxygen atoms; Protons

Electrons

Charge

Symbol

Neutral sodium

11

11

11 – 11 = 0

Na

Sodium cation

11

10

11 – 10 = 1

Na+

Neutral oxygen

8

8

8–8 = 0

Oxygen anion

8

10

8 – 10 = –2

O O2–

4 Monoatomic ions = Ions with only one +

Classify the following atoms as neutral, cation or anion:

–

atom (Na , Cl ...). Diatomic ions = Ions with only two atoms (OH –, NO–...).

a. An b. A

oxygen atom (O) has 10 electrons, 8 neutrons and 8 protons.

potassium atom (K) has 18 electrons, 19 protons and 20 neutrons.

Polyatomic ions = Ions with more than two atoms (SO 4–2 , CO 3–2...). a.

For O, p = 8, e – = 10, n = 8 then p < e– it is an anion. (q = p – e–

b.

ion

q = 8 – 10 = –2)

For K, p = 19, e – = 18, n = 20 then p > e– it is a cation. (q = p – e–

+

⇒

⇒

q = 19 – 18 = +1)

Exercise 3:

Find the cations in the following atoms: A cation

36


a.

Fluorine: 9 e– and 9 p

b.

Gold: 79 p and 78 e –

c.

Zinc: 30 p and 28 e–

3. 3. 5.

AVERAGE ATOMIC MASS

Most of the elements in nature are found as a mixture of isotope atoms.

Natural abundance of isotopes of lithium

Therefore, determining the atomic mass of these elements can be problematic. For example, the lithium atom has two isotopes; 6 Li and 7 Li. So, which number will be the atomic mass of Li, 6 or 7? In fact, the atomic mass of Li is exactly 6.94 amu.

6Li

7.5 %

7Li

92.5 %

To solve this problem, the average atomic masses are utilized. The average atomic mass is the average masses of natural isotopes of an element. The

The average atomic mass of lithium is

average atomic mass is calculated by multiplying the atomic mass of each

6.94

≅

7 amu

isotope by its percentage of abundance and adding the values obtained. This can be shown by the following formula: Average atomic mass = [(The mass of 1st isotope . the % of abundance of the 1st isotope) + (The mass of 2nd isotope . the % of abundance of the 2 nd isotope) + .....]

5 Chlorine 35Cl and 37Cl isotopes are known. What is the average atomic mass of a chlorine atom, if the percentage of abundance of 35Cl is about 75%, and of 37Cl is about 25%?

C h l o enn in o r i r i n n e is yellow ye llow - gre gree color and po isonous gas. poisonous

With the help of t his formula; Average atomic mass = [(The mass of 1st isotope . the % abundance of 1st . isotope) + (the mass of 2 nd isotope . the % abundance of 2nd isotope) + .....] Average atomic mass (Cl) =

amu

6 What is the average atomic mass of Mg, if the natural abundances of Mg isotopes are given below? 24 Mg

: 78.70%

25 Mg

: 10.13%

23 Mg

: 11.17%

Average atomic mass (Mg)= A magnesium, Mg, metal ribbon Introduct�on to Chem�stry

37

1.

Why do we obey safety rules in a school lab? Explain with examples.

14. What is an electron? Explain the difference between valence electrons and other electrons?

2.

In daily life, what is the most common unit that you use?

15. Write the electron configurations for: a. Al13

3.

Name the following glassware.

b. K19

16. What is an ion? How many types of ions can be found? 17. What is atomic number? 18. What is the definition of isotope? 19. What is the smallest subatomic particle known today? Research and discuss the results in class.

  4.

 

 

20. Fill the folllowing table with suitable numbers.

What is the most common type of matter we use in daily life? Discuss in the classroom.

5.

How many states of matter exist? What are the differences between them?

6.

7.

Classify the following as pure substance or mixture. a. Bread

e. Orange juice

b. Jam

f. Snow flake

i. Air

Element Mg Cl S Na

g. Milk

k. Exhaust gas

d. Soap

h. Sea water

l. Carbon dioxide

16 11

n 12 18

charge

12

+1

e– 10

–1 16

A 24 35 32

21. According to the following table, which atoms are isotopes? (Hint: First fill in the blanks)

j. Oxygen

c. Ice (water)

p

Why are some elements (gold and platinum) more

Atom

n

p

X Y Z T

70

66 68

A 139 139 141

73 70

expensive than others (aluminum and iron)? Research. 8.

Look at the periodic table (on pages 92-93) and find the

22. What is the X representation? What information about an atom can it detail?

name of the following elements. 23. Fill in the following blanks. a. He 9.

b. U

c. Ag

d. N

b.

c.

d.

Classify the various homogeneous mixtures according to their physical states and give examples for each.

10. What is the volume of an iron metal bar that weighs 157g? (ρiron = 7.86 g/cm 3) 11. Why do we need to know the melting and the freezing points of substances? 12. What is the atom? Is it the smallest particle in matter? 13. Compare the properties of protons and neutrons. 38

a.


24. What is the average atomic mass? Compare with relative atomic mass. 25. Element X has 3 isotopes. Abundances of these isotopes are given in the following table. Isotopes 20 X 21 X 19 X

Abundance (%) 50% 25% 25%

What is the average atomic mass of X?

1.

6.

Why is chemistry called a unique science? A) Chemistry has many topics.

Which element below is found in its liquid state at room conditions? A) Mer cury

B) Chemists know everything.

B) Aluminum D) Oxygen

C) Chemistry is related with everything around us.

C) Gold

E) Copper

D) Chemists do different experiments everyday. E) Chemistry has branches such as organic, physical, analytical, etc... 7.

Which one(s) of the following statements is/are correct? I. Gases have definite shapes.

2.

II. All liquids flow at the same speed.

Give the right order for the steps in an experiment.

III. Petroleum (raw oil) is a mixture.

I. Recording data II. Conducting experiment

A) I only

III. Setting up experimental equipment

B) II only D) I and II

C) III only E) II and III

IV. Analyzing results A) III, II, I, IV

B) I, II, I II, IV

D) II, IV, III, I

C) II I, II, IV, I

E) IV, III, II, I

8. 3.

A) Table salt

Which is probably not found in a chemistry lab? A) Chemicals

B) Flasks

D) Compass

D) Ammonia

B) 100 cL D) 0.01 daL

5.

C) 10 dL

B) Milk D) Light

E) Bread

What is hard water? A) Solid water

B) Difficult water

C) Water with some ions

D) A type of music

E) Pure water

E) 0.01 hL

10. Which of the following is not a physical property?

Which of the following is not matter? A) Chalk

C) Water

E) Burners

Which is not equal to 1000 mL? A) 1 L

B) Sugar

C) Beakers

9. 4.

Which of the following is not a compound?

C) Snow E) Wood

A) Flammability D) Solubility

B) Boiling Point

C) Density

E) Conductivity Introduction to Chemistry

39

11.

Which of the following statements could be a definition

15.

of a neutral atom? I. An atom having the same number of protons and neutrons.

Which of the following terms is not related to the atom? A) Atomic mass number

B) Atomic number

C) Average atomic mass

D) Relative atomic mass

E) Natural mass

II. An atom having the same number of neutrons and electrons. III. An atom having the same number of electrons and atomic number. 16.

A) I only

B) II only D) I and III

C) II I only

Which of the following atoms are isotopes? ? 16 14

E) II and III

G ,

30 15 ?

H ,

29 ? X 13

A) X and Y

,

28 15 Y ?

B) Y and Z

D) G and H 12.

C) Z and G

E) Z and H

Which of the following atoms has a charge of Z– ? P ____

n ____

e– ____

7

7

10

B) Al : 13

14

10

C) Mg : 12

12

10

D) S : 16

16

18

E) P

16

18

A) N :

: 15

17.

How many energy levels (shells) are there in Na 11? A) 1

18.

B) 2

C) 3

D) 4

E) 5

What is the number of valence electrons in Ca 20? A) 1

13.

30 ?Z 14

,

B) 2

C) 3

D) 4

E) 5

If Y 2+ and Y 2– are ions of atom Y, which of the following is/are always the same for these ions? I. The number of protons II. The number of neutrons

19.

III. The number of electrons A) I only

B) II only D) II and III

A) 24

C) I and I I

One Ba2+ ion has 54 electrons and its atomic mass number is 137. What is the number of neutrons for Ba? A) 80

40

B) 81

B) 28

C) 30

D) 33

E) 35

E) I, II and III

20. 14.

What is the atomic number of an element ha ving a total of 5 electrons in n = 4?

C) 82


D) 83

E) 84

What is amu? A) Atomic master unit

B) Atomic microbes unit

C) Atomic unit

D) Atomic mass unit E) Atom massive unit

INTRODUCTION The modern periodic table appeared as a function of the physical and chemical properties of elements. When the elements are arranged in the order of increasing atomic numbers, there is a periodic repetition in the properties of these elements. A simple periodic table contains the symbols, atomic numbers and the relati ve atomic masses of the elements. Additionally, detailed periodic tables containing some physical and chemical properties (such as melting point, boiling point, oxidation state) are also made. Each horizontal row in the periodic table is called a period. There are seven periods in the modern periodic table and each period begins with a metal and ends with a noble gas. However, the first element of the first period (hydrogen) is not a metal. AdditiPeriod

The first element

The last element

Number of elements

1st period

1H

2He

2

2nd period

3Li

10Ne

8

3rd period

11Na

18 Ar

8

4th period

19K

36Kr

18

5th period

37Rb

54 Xe

18

6th period

55Cs

86Rn

32

7th period

87Fr

The first element, the last element and the number of elements in each period in the periodic table.

onally, the noble gas of the se venth period has not been disco vered yet. Each vertical column in the periodic table is called a group. Since the chemical and physical properties of the elements in a group are similar, they are sometimes also called a family . There are a total of eighteen groups in the periodic table of which eight are A groups and eight are B groups. The group 8B contains three columns. A groups are called main groups (representati ve group) and B groups are called transition metals.

1. THE PERIODIC TABLE AND ELECTRON CONFIGURATION The physical and chemical properties of the elements are directly related to their electron configurations. For example, chemical properties such as gaining, gi ving and sharing of electrons are dependent on the valence electrons and nucleus structure. As a result, chemical beha viors of the elements are closely related to the nucleus structure and electron configuration of the element. Elements in the same period contain different numbers of electrons in the valence shells.

Electron configurations of the elements in the second period

For this reason, elements in the same period ha ve different physical and chemical properties. The valence electron configurations of the elements in the same group are the The elect ron confi gu rations of the ele ments in group 1A end with s 1 and the ele ments in group 2A end with s2. 42


same. Therefore, elements in the same group show similar chemical beha viors in a chemical reaction, but their physical properties may gradually change.

Dmitri Ivanovich Mendeleev (1834-1907) Mendeleev, the youn gest of a fa mily of seventeen, was born in To bolsk, Si be ria. His fat her was the di rector of a high school and his grandfat her was the as sistant of the first jour nalist in Si be ria. After his fat her died, his mot her moved to St. Peters burg to give him the best pos sible education.

him a world fa mous che mist in the field of the periodic table. His ot her studies, collected in 25 books, are very inte resting as well. He organized knowled ge on iso morp hism, a study which sup ported the develop ment of geoc he mistry. Furthermore, he fo und the critical po int and develo ped the “hydrate theory”, which made him a gre at physical che mist.

Dmit ri proved his worth in St. Peters burg when he pre pa red a the sis “The Com bi nation of Alco hol and Water” (1856). Mendeleev met and wor ked with Bun sen and a lot of Western scientists, and partici pated in the Karls ru he confe rence in Ger many (1858). At this confe rence, the re was inten sive discus sion about Avo gad ro’s hypot he sis. Dimitri then vi sited Pennsylva nia to see the

Mendeleev was a mem ber of about 70 acade mic and scientific com mittees. He regarded, his first res pon si bility as re se arch and his second res pon si bility as le ar ning. He wor ked as a te ac her in most of the schools in St. Peters burg. When Mendeleev publis hed his pe riodic

first oil wells. After retur ning to Rus sia, he develo ped a new com merci al distillation system when he was 32 ye ars old. Mendeleev was ap po inted profes sor of inor ga nic che mistry at St. Peters burg Univer sity. His most important study was the pe riodic table that he develo ped using the re gula rities of che mical and physical pro perties of the ele ments.

table for the first ti me, the re we re 63 ele ments. After his death, the num ber of ele ments had inc re ased to 86. This qu ick inc re ase was the re sult of the pe riodic table, the most im portant systemization of che mistry. Alt hough Mendeleev did not discover any new ele ments, the ele ment with the ato mic num ber 101 discove red by a

In this study, Mendeleev esti mated the existence of so me ele ments which had not yet been discove red. The discovery, a few ye ars later, of ele ments he had esti mated made

com mittee of Ame rican scientists led by G.T Se aborg in 1955, was na med mendelevium (Md) in ho nor of Dmit ri Mendeleev.

1. 1. GROUPS The periodic table contains the elements of the groups A and groups B. Among the elements of the groups A, group 1A and 2A elements belong to the s–block and group 3A, 4A, 5A, 6A, 7A and 8A elements belong to the p–block. The elements of the groups B belong to the d–block (transition metals) and f–block (inner transition metals). In the periodic table, each A group has a special name.

Families and the s, p, d, f blocks in the periodic table Periodic Table

43

Now let’s examine the properties of some groups in the periodic table. Group 1A : Alkali Metals (ns1) This group contains the elements hydrogen (H), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Although hydrogen is a non-metal, it is placed in this group because of its electron configuration, 1s1. Alkali metals are chemically the most acti ve metals. They ha ve only one electron in their valence orbitals and their electron configuration ends with ns1. They become positive one charged ions easily by gi ving off this valence electron in chemical reactions. In nature, the hydrogen molecule occurs in a diatomic structure (H2). It is in a gaseous state at room temperature. Hydrogen, whose characteristics are predominantly non-metallic, has a negative one charge in some compounds. All other members of this group, ha ving the typical metallic characteristics, are solid at room temperature. Francium is only radioactive element in this group. Group 2A : Alkaline Earth Metals (ns2) Alkali metals (group 1A) and alkaline earth metals (group 2A)

This group contains the elements beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). After the alkali metals, they are the second most acti ve metals. Their electron configurations end with ns2. They become positive two charged ions by gi ving of their two valence electrons in chemical reactions. At room temperature, they occur in a monoatomic structure and they are solid at room temperature. Radium, a solid element, is the only radioactive member of this group. Group 7A: Halogens (ns2 np5) This group contains the elements fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine (At). These elements occur naturally in a diatomic structure (F2, Cl2, Br2, I2, At2). Fluorine and chlorine are gases, bromine is a liquid and iodine is a solid. Astatine is a radioactive and solid element. Halogens are the most acti ve nonmetals. Therefore, they become negative one charged ions by gaining an electron to complete their valence shell in the chemical reactions. Group 8A: Noble Gases (ns2np6) This group contains the elements helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn). Their electron configurations end with ns2np6,

Halogens (group 7A) and noble gases (group 8A)

except helium, which ends with ns 2. Since their valence shells are full, they ha ve no chemical acti vity and they are called noble gases or inert gases. They are the most stable elements in nature. Therefore, all other elements try to make their electron configurations similar to noble gases; either by gaining or losing electrons electrons. They occur in a monoatomic structure as colorless gases with lo w freezing points at room temperature.

44


1. 2. ELECTRON CONFIGURATION Rules of Electron Distribution Pauli’s Principle The electron of a hydrogen atom in its ground state is located in the nearest orbital to the nucleus. But, what about the electron distribution of the atoms with more than one electron? Ans wering this question in 1925, Wolfgang Pauli stated his exclusion principle thus: ‘In the same atom, two electrons may not ha ve identical sets of all quantum numbers.’ According to this principle, the quantum numbers, n, l, ml, and ms, can ne ver be identical for two electrons in an atom. This means that at least one of the quantum numbers must be different. For example, even if two electrons ha ve identical values for n, l and m l (as a result of being in the same orbital), their magnetic spin quantum numbers must be different. That is, these electrons are said to ha ve opposing spins. In fact, we ha ve already mentioned that each electron may be described by a set of the four quantum numbers; – n shows the shell and the relati ve average distance of the electron from the nucleus – l shows the subshell and the shape of the orbital for the electron – ml represents the orientation of the orbital in spaces

Wolf gang Pauli (1900 – 1958) Pauli, an Austri an physicist, is best known for his exclu sion principle regarding the distri bution of electrons among the atomic or bitals, for which he was awarded the 1945 No bel Physics Pri ze. In his exclu sion principle, Pauli says that no two electrons in the same atom may have identical sets of all four quan tum num bers.

– ms refers to the spin of the electron. The Aufbau Principle The Aufbau principle basically states that the lowest energy orbitals are filled first. 1s orbital has the lowest energy, so it is first to be filled, followed, in order, by 2s, 2p, 3s... This ordering was first stated by Wolfgang Pauli and is called the Aufbau principle (aufbau means ‘building up’ in German).

Ground state: The state in which all the electrons in an atom are in the lowest energy levels available. For example, 2 2 6 2 12 Mg: 1s 2s 2p 3s

Hund’s Rule Different orbitals with identical energy (those in the same subshell) are known as

to be as far as possible from each other. Thus, Hund’s rule states that the

Excited state electron configuration: When an atom has absorbed energy, its electrons may move to higher state energy levels. For example, 12 Mg: 1s 2

electrons are distributed among the orbitals of a subshell of the same energy in

2s 2 2p6 3s1 3p1

equal energetic orbitals. For example the orbitals of p subshell p x , p y and pz are of identical energy. Since all electrons carry the same electrical char ge, they tend

a way that gi ves the ma ximum number of unpaired electrons with parallel spin. The term ‘parallel spin’ means that all the unpaired elect rons spin in the same direction, and all of the m s values of these electrons ha ve the same sign. In some cases, at higher quantum le vels, since the energies of some subshells

Aufbau principle (Aufbau process) is also called Aufbau order.

are very close to each other, there may not be any coherence bet ween the order of filling the orbitals and the order of increasing the energies of the orbitals. For Periodic Table

45

example, the 4s orbital has a lo wer energy than that of a 3d orbital. That is, the 4s orbital is filled before the 3d orbital. The order of filling of orbitals is deri ved as a result of experiments in spectroscopy and magnetism. The order of filling electrons in atomic orbitals, with a few exceptions, is roughly as follows. 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s2, 4f 14, 5d10, 6p6, 7s2, 5f 14, 6d10, 7p6 In order to remember and deri ve this order easily, the method illustrated by the table below left is very useful. When following the arrows from top to bottom, the order gi ven abo ve is obtained.

Representation of Electron Configuration The electron configuration of an atom can be represented by either electronic notation (s, p, d, f) or by orbital diagram. 

For instance, the electron configuration of the silicon, Si, atoms for which the

General order of filling of the orbitals in an atom.

atomic number is 14 (that is, the number of electrons is 14) is gi ven below. Si: 1s2 2s2 2p6 3s2 3p2 Orbital diagram notation :

Si 





p x p y



pz



p x p y pz

In the orbital diagram notation, each subshell is divided into indi vidual orbitals drawn as bo xes. An arrow pointing up ward corresponds to one type of spin (+1/2) and an arrow pointing down corresponds to the opposite spin (–1/2). Elect rons in the same orbital with opposed spins are said to be paired, such as the electrons in the 1s and 2s orbitals. These orbitals are completely filled orbitals. On the other hand, since electrons are placed one by one in a subshell with parallel spins, the corresponding arrows are drawn in the sa me direction, such as in the 3p electrons of the silicon atom. Such orbitals are half–filled orbitals.

The Aufbau order of filling the atomic orbitals.

46


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