Basic Trends Across the Periodic Table 1) Draw a line in the the middle middle of a piece of graph graph paper, separating the page into top and bottom. On the top, plot a graph of number of outer electrons and, in the same coordinate system, a second graph of number of protons (y-axis) vs. atomic number (x-axis). On the bottom plot a separate graph of atomic radius vs. atomic number. For each graph connect successive dots with straight lines. Also, ensure that identical atomic numbers are plotted on the same vertical position on the sheet (i.e. atomic number 1 in the top graph should be on the same line as atomic number 1 in the bottom graph). 2) Examine your your graph of electron number number vs. atomic number. a) Which elements elements are found found at the main peaks on your graph (there should be 3)? What do these elements have in common? b) Which elements elements are found found at the main valleys on your graph (there should be 3)? What do these elements have in common?
Atomic Number
Element Symbol
Number of Protons
Number of Outer Electrons
Atomic Radius
1
H
1
1
32
2
He
2
2
31
3
Li
3
1
123
4
Be
4
2
90
5
B
5
3
82
6
C
6
4
77
7
N
7
5
75
8
O
8
6
73
9
F
9
7
72
10
Ne
10
8
71
11
Na
11
1
154
12
Mg
12
2
136
13
Al
13
3
118
14
Si
14
4
111
15
P
15
5
106
16
S
16
6
102
17
Cl
17
7
99
18
Ar
18
8
98
19
K
19
1
203
20
Ca
20
2
174
3) Examine your your graph of atomic radius radius versus atomic number. a) Which elements are found at the peaks peaks on your graph? graph? What do these elements have in common? b) Which elements are are found at the valleys on your graph? What What do these elements have in common?
4) How are proton number number and atomic atomic radii related (i.e. as the proton number number increases, what happens to the atomic radius)? Use this to explain the trends in atomic radius across a period. 5) Generally, as you go from left to right across a period on on the periodic table, table, what happens to atomic radius? 6) Generally, as you go down a group group in the periodic table, what happens to atomic atomic radius? 7) Why does radius radius increase as you go down a group? Sum up your results to be able to present them to your classmates: 1. Going across across a period, period, the atomic atomic radius radius ______ __________ ________ ________ _____. _. 2. As you you move move from from left to to right right across across a period period the numbe numberr of _________________ _________________ in the _______________ _______________ increases, so that there is an _________________ __________________ _ in nuclear charge. 3. The added added extra extra electrons electrons go into into the _______ ___________ ________ _____ _ outer shell. shell. 4. The increasing increasing _______ ___________ ________ ____ _______ __________ _______ _______ ___ attracts attracts the outer outer electrons more strongly moving across the period, so ____________________ ____________________ the atomic radius of the elements.
Basic Trends Across the Periodic Table 1) Draw a line in the middle of a piece of graph paper, separating the page into top and bottom. On the top, plot a graph of number of outer electrons (yaxis) vs. atomic number (x-axis). On the bottom plot a separate graph of melting point vs. atomic number. For each graph connect successive dots with straight lines. Also, ensure that identical atomic numbers are plotted on the same vertical position on the sheet (i.e. atomic number 1 in the top graph should be on the same line as atomic number 1 in the bottom graph). In your graph, colour the dots for the metallic elements, the semi-metallic elements, and the non-metallic elements in different colours 2) Examine your graph of electron number vs. atomic number. a) Which elements are found at the main peaks on your graph (there should be 3)? What do these elements have in common? b) Which elements are found at the main valleys on your graph (there should be 3)? What do these elements have in common? 3) Examine your graph of melting points versus atomic number. a) Which elements are found at the peaks on your graph? What do these elements have in common? b) Which elements are found at the valleys on your graph? What do these elements have in common? 4) How are outer electron numbers, metallic character and melting points related (i.e. as the outer electron number increases in metals, what happens to the melting point)? 5) Generally, as you go from left to right across a period on the periodic table, what happens to the melting points?
Atomic Number
Element Symbol
Number of Outer Electrons
1
H
1
2
He
2
3
Li
4
Be
Type of element
Melting point/ °C
nonmetal nonmetal
259,14
1
metal
180,54
2
metal
1278
nonmetal nonmetal nonmetal nonmetal nonmetal nonmetal
-272
5
B
3
6
C
4
7
N
5
8
O
6
9
F
7
10
Ne
8
11
Na
1
metal
97,8
12
Mg
2
metal
650
13
Al
3
metal
660,37
14
Si
4
semimetal
1410
5
nonmetal
44,1
6
nonmetal
112,8
15
16
P (molecule s of 4 P atoms) S (molecule s of 8 S atoms)
17
Cl
18
Ar
19
K
20
Ca
3500 -209,9 -218,4 219,62 -248,6
nonmetal nonmetal
100,98
1
metal
63,65
2
metal
839
7
2300
8
-189
6) Generally, as you go down a group in the periodic table, what happens to the melting points? 7) Which type of structures do you find as you go across the period? Use this to explain the trends in melting point across a period. Why do phosphorus and Sulphur not follow the trend of nitrogen and oxygen?
Sum up your results to be able to present them to your classmates:
1. Metallic properties ______________ as you move from left to right across the period. 2. Melting points _____________ from sodium to aluminium because the number of _________ _____________ increases and there are more delocalised electrons that form a stronger metallic bond. 3. Metals are ______________ electrical conductors than non-metals. 4. The melting point of phosphorus is ______________ than sulphur’s melting point because the molecules of phosphorus consist of __________ atoms than the sulphur molecules and thus have less van-der-Waals forces.
Atomic radii, numbers of protons and numbers of electrons
1. Going across a period, the atomic radius ___________________. 2. As you move from left to right across a period the number of _________________ in the _______________ increases, so that there is an __________________ in nuclear charge. 3. The added extra electrons go into the ________________ outer shell. 4. The increasing _______________ _________________ attracts the outer electrons more strongly moving across the period, so ____________________ the atomic radius of the elements.
Metallic properties, electric conductivity and melting points
1. Metallic properties ______________ as you move from left to right across the period. 2. Melting points _____________ from sodium to aluminium because the number of _________ _____________ increases and there are more delocalised electrons that form a stronger metallic bond. 3. Metals are ______________ electrical conductors than non-metals. 4. The melting point of phosphorus is ______________ than sulphur’s melting point because the molecules of phosphorus consist of __________ atoms than the sulphur molecules and thus have less van-der-Waals forces.
