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Atomic Structure
Investigation 4B
Modeling the Location of an Electron in an Atom Background Information
. d e v r e s e r s t h g i r l A l . a H e c i t n e r P n o s r a e P s a g n i h s i l b u p , . c n I , n o i t a c u d E n o s r a e P ©
In the atomic models of the early twentieth century, century, electrons were said to move around the nucleus along specific paths, much as the planets move around the sun. However, However, experimental evidence has indicated that the precise position of an electron in an atom cannot cann ot be known or predicted. Scientists can speak only of the probability of finding electrons at various locations, not of their exact positions. Probability is a measure of how often a certain event will occur out o ut of a total number of events. For example, there are two ways a coin can land—with its head facing up or its tail facing up. Each side has a 50 percent (or one out of two) probability of landing face up for any toss. An electron cloud provides a visual model for the probable behavior of an electron in an Nucleus atom. The electron cloud shows the likelihood that an electron will be found in a given part of the atom around the nucleus. If the electron is not likely to be found at a particular position, the cloud appears less dense. If the electron is more likely to be found at a particular position, the cloud has a denser appearance, as shown in Figure 1. In this investigation, you will use probability to describe the location of an electron in an atom. a tom.
Electron cloud
Figure 1
Problem How can the location of an a n electron in an atom be described?
Pre-Lab Discussion Read the entire investigation. Then, work with a partner to answer the following questions. 1. Applyin Applying g Concept Conceptss Scientists use probability to predict the behavior of electrons in an atom. What is probability?
Probability is is a measure of how often a certain cer tain event will will occur out of a total number nu mber of events.
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Name ___________________________
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2. Applying Concepts According to the way you will mark your die at the beginning of this investigation, what is the probability of the electron being found in the zone closest to the “nucleus” (0–4 cm)? In the second closest zone (4–6 cm)? In the third closest zone (6–8 cm)?
The probabilty of landing in the 0-4cm is 1 in 6, landing in the 4 6cm is 4 in 6, and landing in the 6 to 8cm is 1 in 6. 3. Predicting Describe the results you expect to observe.
There will be more electrons in the 4 to 6 cm area.
4. Inferring What can you infer about the probable locations of an electron in an atom from the above prediction?
That the majority of them are in the second ring.
5. Comparing and Contrasting Do you expect your results to be identical to those of other students, or similar to those of other students, or completely different from those of other students? Explain your answer.
Simillar because they should be somewhat relevant to others electrons.
Materials
(per group)
game die masking tape graph paper pencil red pencil metric ruler
Procedure 1. Cover all six sides of the die with masking tape. Mark one of the sides with one dot, four of the sides with two dots each, and the remaining side with three dots. 2. Select a square near the center of the graph paper and use a red pencil to color it red. This red square will represent the nucleus of a hydrogen atom with one electron. 44
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Investigation 4B
© P e a r s o n E d u c a t i o ,n I n c . , p u b l i s h i n g a s P e a r s o n P r e n t i c e H a l .l A l l r i g h t s r e s e r v e d .
Name ___________________________
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3. Toss the die. Use a regular pencil to color in a square according to the following rules: If the number 1 appears face up on the die, color in any square that is between 0 cm and 4 cm from the “nucleus.”
If the number 2 appears face up on the die, color in any square that is between 4 cm and 6 cm from the “nucleus.” If the number 3 appears face up on the die, color in any square that is between 6 cm and 8 cm from the “nucleus.” 4. Repeat Step 3, tossing the die and marking the graph for a total of 50 tosses. Record your results in the data table.
Observations DATA TABLE Distance from “Nucleus”
Number of Colored-in Squares
0–4 cm
10
4–6 cm
35 6–8 cm
5 . d e v r e s e r s t h g i r l A . l a H e c i t n e r P n o s r a e P s a g n i h s i l b u p , . c n I , n o i t a c u d E n o s r a e P ©
Analysis and Conclusions 1. Observing In which zone are most of the colored-in squares on your diagram?
4-6cm 2. Using Models What does each colored-in square on your diagram represent?
an electron 3. Inferring Based on your data, where would you be most likely to find an electron? Explain your answer.
the second ring because that is wear the majority of the
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Name ___________________________
Class ___________________
Date _____________
4. Comparing and Contrasting Compare your diagram to a classmate’s. Are they identical? In what ways are they alike or different?
yes the majority of them reside in the second
5. Drawing Conclusions Can the exact position of an electron in an atom be determined? What can you know about an electron’s location?
No becasue it is to small. That them majority of them reside in the second
6. Predicting Suppose you had tossed the die 100 times. How do you think your results would have compared with the results you obtained by tossing the die 50 times?
The majority of them would still reside in the second ring aprox. 70 of them and 20 in the first ring and 10 in the last
Go Further Redesign the procedure in this investigation to model the behavior of the two electrons in a helium atom. Can the electrons be in the same location at the same time? Can they be in the same location at different times? Describe the modified procedure and the results you might expect.
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© P e a r s o n E d u c a t i o ,n I n c . , p u b l i s h i n g a s P e a r s o n P r e n t i c e H a l .l A l l r i g h t s r e s e r v e d .
