1. Periodic Trends in the Properties of the Elements

2. Reactivity
Metals: as you move down a family, reactivity goes up. As you move across a period, reactivity goes down.
Brainiac’s Video
Nonmetals: as you move down a family, reactivity goes down. As you move across a period, reactivity goes up.
Except for the Noble Gases!!!!

3. Atomic Size Either volume or radius.
Treat atom as a hard marble.
As you move down a column on the periodic table, the size of the atom increases.
Valence shell farther from nucleus.
As you move left to right across a period, the size of the atom decreases.
Adding electrons to same valence shell.
Valence shell held closer.

4. Trends in Atomic Size, Continued

5. Be (4p+ and 4e-) Mg (12p+ and 12e-) Ca (20p+ and 20e-) Group IIA 2e-

6. Li (3p+ and 3e-) Be (4p+ and 4e-) B (5p+ and 5e-) C (6p+ and 6e-)
Period 2
2e-
1e-
3 p+
2e-
4 p+
2e-
3e-
5 p+
Li (3p+ and 3e-)
Be (4p+ and 4e-)
B (5p+ and 5e-)
6 p+
2e-
4e-
8 p+
2e-
6e-
10 p+
2e-
8e-
C (6p+ and 6e-)
O (8p+ and 8e-)
Ne (10p+ and 10e-)

7. Choose the Larger Atom in Each Pair
C or O
Li or K
C or Al
Se or I?

8. Practice—Choose the Larger Atom in Each Pair.
1. N or F
2. C or Ge
3. N or Al
4. Al or Ge

9. Practice—Choose the Larger Atom in Each Pair, Continued.
N or F, N is further left
N or F
C or Ge
N or Al, Al is further down & left
N or F
C or Ge, Ge is further down
N or F
C or Ge
N or Al
Al or Ge? opposing trends

10. Ionization Energy
Minimum energy needed to remove an electron from an atom.
Valence electron easiest to remove.
M(g) + 1st IE  M1+(g) + 1 e-
M+1(g) + 2nd IE  M2+(g) + 1 e-
First ionization energy = energy to remove electron from neutral atom; 2nd IE = energy to remove from +1 ion; etc.

11. Trends in Ionization Energy
As you move down a family, the IE gets smaller.
Valence electron farther from nucleus.
As you move left to right across a period, the IE gets larger.

12. Trends in Ionization Energy, Continued

13. Example—Choose the Atom in Each Pair with the Higher First Ionization Energy
Al or S, Al is further left
1. Al or S
2. As or Sb
3. N or Si
4. O or Cl, opposing trends
Al or S
As or Sb
N or Si, Si is further down and left
Al or S
As or Sb, Sb is further down

14. Practice—Choose the Atom with the Highest Ionization Energy in Each Pair
1. Mg or P
2. Cl or Br
3. Se or Sb
4. P or Se

15. Practice—Choose the Atom with the Highest Ionization Energy in Each Pair, Continued
1. Mg or P
2. Cl or Br
3. Se or Sb
4. P or Se ?

16. Metallic Character
How well an element’s properties match the general properties of a metal.
In general, metals are found on the left of the periodic table and nonmetals on the right.
As you go left to right across the period, the elements become less metallic.
As you go down a column, the elements become more metallic

17. Trends in Metallic Character

19. Example—Choose the More Metallic Element in Each Pair
Sn or Te, Sn is further left
Sn or Te
P or Sb
Ge or In
S or Br? opposing trends
Sn or Te
P or Sb
Ge or In, In is further down & left
Sn or Te
P or Sb, Sb is further down

20. Practice—Choose the More Metallic Element in Each Pair
Sn or Te
Si or Sn
Br or Te
Se or I

21. Practice—Choose the More Metallic Element in Each Pair, Continued
Sn or Te
Si or Sn
Br or Te
Se or I ?

22. Electronegativity
Measure of the pull an atom has on bonding electrons.
Increases across the period (left to right).
Decreases down the group (top to bottom).
The larger the difference in electronegativity, the more polar the bond.
Negative end toward more electronegative atom.
d+ H — F d-

23. Electronegativity, Continued
2.1
1.0
0.9
0.8
0.7
1.5
1.2
1.3
1.1
1.4
1.6
1.8
1.7
1.9
2.2
2.4
2.0
2.5
3.0
3.5
4.0
2.8

24. Electronegativity, Continued

25. Melting/Boiling Point
High melting/boiling point indicates strong bonding
Middle of Periodic Table
Low melting/boiling point indicates weak bonding
Lowest MP/BP across period indicates completely filled orbital
Edges of Periodic Table
Noble gases have no bonding forces
MP/BP unusually low

26. Melting/Boiling Point