Periodic Relationships Among the Elements CHEMISTRY 161 Chapter 8 Periodic Relationships Among the Elements www.chem.hawaii.edu/Bil301/welcome.html

REVISION high EA low IE

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

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

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

Group 1 (ns1, n2)

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)

Group 2 (ns2, n2)

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

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

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)

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

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

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

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

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

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

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

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

Oxides molecular ionic three dimensional discrete units

Oxides basic amphoteric acidic

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)

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)

SUMMARY

Homework Chapter 8 pages 310-322, problem sets