1. Periodic Relationships Among the Elements
CHEMISTRY 161
Chapter 8
Periodic Relationships Among the Elements

2. REVISION
high EA
low IE

3. d- and f-shell contraction 2. half and fully occupied shells
EXCEPTIONS
d- and f-shell contraction
2. half and fully occupied shells

4. diagonal relationships
5. Trends in Chemical Reactivity
diagonal relationships
charge density

5. Hydrogen (1s1) H → H+ + e- group 1 acids group 7 hydrides (LiH, CaH2)
H + e- → H- +1 -1
LiH + H2O → LiOH + H2

6. Group 1 (ns1, n2)

7. 2 M(s) + 2 H2O(l) → 2 MOH(aq) + H2(g) 2 M(s) + 1/2 O2(g) → M2O(s)
1. low ionization energies → very reactive
2. react with water and form hydrogen
2 M(s) + 2 H2O(l) → 2 MOH(aq) + H2(g)
3. react with oxygen and form oxides
2 M(s) + 1/2 O2(g) → M2O(s)
M2O2 (peroxides)
K, Rb, Cs, (Fr)
MO2 (superoxides)

8. Group 2 (ns2, n2)

9. M(s) + 2 H2O(l) → M(OH)2(aq) + H2(g) M(s) + 1/2 O2(g) → MO(s)
1. higher ionization energies → less reactive
2. react slowly with water and form hydrogen
M(s) + 2 H2O(l) → M(OH)2(aq) + H2(g)
M = Mg, Ca, Sr, Ba, (Ra)
3. react with oxygen and form oxides
M(s) + 1/2 O2(g) → MO(s)
M = Ba, Sr, (Ra)
MO2 (peroxides)
90Sr versus Ca

10. Group 3 (ns2np1, n2)
semi metal
(unreactive to water and oxygen)

11. 4 M(s) + 3 O2(g) → 2 M2O3(s) 2 M(s) + 6 H+(aq) → 2 M3+(aq) + 3 H2(g)
1. react with oxygen and form oxides
4 M(s) + 3 O2(g) → 2 M2O3(s)
2. M (M = Ga, In, Tl) can be +3 and +1
stability of +1 increases from Ga via In to Tl
3. react with acids and form hydrogen
2 M(s) + 6 H+(aq) → 2 M3+(aq) + 3 H2(g)
4. covalent versus ionic compounds
(hydrides AlH3 and BeH2)

12. Group 4 (ns2np2, n2)
semi metal
(no reaction with water)

13. E(s) + O2(g) → EO2(g/s) M(s) + 2 H+(aq) → M2+(aq) + H2(g)
1. react with oxygen and form oxides
E(s) + O2(g) → EO2(g/s)
2. E can be +4 and +2
stability of +2 increases from C to Pb
CO2/CO; SiO2/SiO; PbO2/PbO
3. react with acids and form hydrogen
M(s) + 2 H+(aq) → M2+(aq) + H2(g)
4. covalent versus ionic compounds

14. oxidation numbers; oxides; oxoacids
Group 5 (ns2np3, n2) N2 P4
semi metal
oxidation numbers; oxides; oxoacids

15. oxidation numbers;oxoacids
Group 6 (ns2np4, n2) O2 S8
Se8
semi metal
oxidation numbers;oxoacids

16. oxidation numbers; oxoacids
Group 7 (ns2np5, n2)
oxidation numbers; oxoacids

17. 1. all elements exist as diatomic species X2
2. high electron affinities
X + e- → X-
isoelectronic with noble gases
3. react with hydrogen
X2 + H2 → 2 HX
acidity increases from HF to HI

18. Group 8 (ns2np6, n2)
Group 8 (ns2np6, n2)
monoatomic species

19. XePtF6, XeF4, XeO3, XeO4 low reactivity KrF2 HArF
ionization energy decreases

20. Oxides
molecular
ionic
three dimensional
discrete units

21. Oxides
basic
amphoteric
acidic

22. Na2O(s) + H2O(l) → 2 NaOH(aq)
basic
Na2O(s) + H2O(l) → 2 NaOH(aq)
2 MgO(s) + 2 H2O(l) → 2 Mg(OH)2(aq)
MgO(s) + 2 HCl(l) → MgCl2(aq) + H2O(l)
acidic
CO2(g) + H2O(l) → H2CO3(aq)
P4O10(s) + 6 H2O(l) → 4 H3PO4(aq)
SO3(s) + H2O(l) → H2SO4(aq)
Cl2O7(s) + H2O(l) → 2 HClO4(aq)

23. Al2O3(s) + 6 HCl(l) → 2 AlCl3(aq) + 3 H2O(l)
amphoteric
Al2O3(s) + 6 HCl(l) → 2 AlCl3(aq) + 3 H2O(l)
Al2O3(s) + 2 NaOH(aq) + 3 H2O → 2 Na[Al(OH)4](aq)

24. SUMMARY

25. Homework
Chapter 8
pages , problem sets