1. Periodic Relationships Among the Elements
Chapter 7
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2. When the Elements Were Discovered
8.1

3. Atomic radius – one-half the distance between the two nuclei in two adjacent metal atoms or in a diatomic molecule
8.3

4. 8.3

6. General Trend in First Ionization Energies
Increasing First Ionization Energy
Increasing First Ionization Energy
8.4

7. Electron affinity is the negative energy change that occurs when an electron is accepted by an atom in the gaseous state to form an anion.
X (g) + e X-(g)
F (g) + e F-(g)
DH = -328 kJ/mol
EA = +328 kJ/mol
O (g) + e O-(g)
DH = -141 kJ/mol
EA = +141 kJ/mol
8.5

8. Electron affinity – the energy change in kJ accompanying the addition of 1 mol of e- to 1 mol of gaseous atoms or ions.

9. SAMPLE PROBLEM
Ranking Elements by Atomic Size
PROBLEM:
Using only the periodic table (not Figure 8.15)m rank each set of main group elements in order of decreasing atomic size:
(a) Ca, Mg, Sr
(b) K, Ga, Ca
(c) Br, Rb, Kr
(d) Sr, Ca, Rb
PLAN:
Elements in the same group increase in size and you go down; elements decrease in size as you go across a period.
SOLUTION:
(a) Sr > Ca > Mg
These elements are in Group 2A(2).
(b) K > Ca > Ga
These elements are in Period 4.
(c) Rb > Br > Kr
Rb has a higher energy level and is far to the left. Br is to the left of Kr.
(d) Rb > Sr > Ca
Ca is one energy level smaller than Rb and Sr. Rb is to the left of Sr.

10. SAMPLE PROBLEM
Ranking Elements by First Ionization Energy
PROBLEM:
Using the periodic table only, rank the elements in each of the following sets in order of decreasing IE1:
(a) Kr, He, Ar
(b) Sb, Te, Sn
(c) K, Ca, Rb
(d) I, Xe, Cs
PLAN:
IE decreases as you proceed down in a group; IE increases as you go across a period.
SOLUTION:
(a) He > Ar > Kr
Group 8A(18) - IE decreases down a group.
(b) Te > Sb > Sn
Period 5 elements - IE increases across a period.
(c) Ca > K > Rb
Ca is to the right of K; Rb is below K.
(d) Xe > I > Cs
I is to the left of Xe; Cs is furtther to the left and down one period.

11. Group 1A Elements (ns1, n  2)
8.6

12. Increasing reactivity
Group 1A Elements
Increasing reactivity
Low Ionization energies.
Tendency to lose the single valance electron
They are very reactive, never found in nature in pure state
8.6

13. Group 2A Elements (ns2, n  2)
8.6

14. Increasing reactivity
Group 2A Elements
Increasing reactivity
Alkaline earth metals
Metallic character increases from top to bottom
8.6

15. Group 3A Elements (ns2np1, n  2)
8.6

16. Group 3A Elements
Boron is a metalloid; the rest are metals
8.6

17. Group 4A Elements (ns2np2, n  2)
8.6

18. Group 4A Elements Carbon a non metal
Silicon and Germanium are metalloids
Then all metals
8.6

19. Group 5A Elements
8.6

20. Group 5A Elements Nitrogen and Phosphorous are non metals
Arsenic and antimony are metalloids
Bismuth is a metal
8.6

21. Group 6A Elements
8.6

22. Group 6A Elements The 1st three are non metals
The last two are metalloids
8.6

23. Group 7A Elements
8.6

24. Increasing reactivity
Group 7A Elements
Increasing reactivity
All are halogens and are non metals
Great reactivity
Never found in their element form in nature
High ionization energies
Large positive electron affinity
8.6

25. No tendency to accept extra electrons.
Group 8A Elements
Completely filled ns and np subshells. Highest ionization energy of all elements.
No tendency to accept extra electrons.
8.6

26. Trends in metallic behavior.