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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 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 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 atomic radius 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 proton number and atomic radii related (i.e. as the proton 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 the periodic table, what happens to atomic radius?
6) Generally, as you go down a group in the periodic table, what happens to atomic radius?
7) Why does radius increase as you go down a group?
Sum up your results to be able to present them to your classmates:
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.
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
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 (y-axis) 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?
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
Atomic Number
Element Symbol
Number of Outer Electrons
Type of element
Melting point/
°C
1 H 1 non-metal
-259,14
2 He 2 non-metal -272
3 Li 1 metal 180,54
4 Be 2 metal 1278
5 B 3 non-metal 2300
6 C 4 non-metal 3500
7 N 5 non-metal -209,9
8 O 6 non-metal -218,4
9 F 7 non-metal
-219,62
10 Ne 8 non-metal -248,6
11 Na 1 metal 97,8
12 Mg 2 metal 650
13 Al 3 metal 660,37
14 Si 4 semi-metal 1410
15
P (molecules of 4 P atoms)
5 non-metal 44,1
16
S (molecules of 8 S atoms)
6 non-metal 112,8
17 Cl 7 non-metal
-100,98
18 Ar 8 non-metal -189
19 K 1 metal 63,65
20 Ca 2 metal 839
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.