Ch 16. Group 16

O allotropes O2: Ground state is a paramagnetic gas BP = -183 C (blue liquid) 3/2 O2 (g)  O3(g) ΔGf = +163 kJ/mol Ozone is a strong oxidant!

Na (liq) + Sn(liq)  NaSn S allotropes S: ring structures S6 to S20 with S8 most common S8 --> Sn (a red, viscous, elastomeric helical polymer) Sn is metastable at RT, reverts to S8 application: Na/S battery uses a molten S anode Na (liq) + Sn(liq)  NaSn

Elemental forms S82+ S8 + 3AsF5  (S8)(AsF6)2 + AsF3 bright red solution 4 Se + S2O6F2  (Se4)(SO3F)2 Se42+ is a square planar ring HSO3F S-S ~ 0.19-0.21 nm transannular bond ~ 0.28 nm Se Te Po increasing metallic character Se (m) is a semiconductor, photoconductor, bandgap ~ 1.8 eV Po is metallic, primitive cubic structure, radioactive with max body burden = 7x1012g (20 trillion atoms) S82+

S halides C2

S halides C2v C2v

S halides Oh kinetically stable against hydrolysis

Frost diagrams

S oxides generally mild oxidants or mild reducing agents, i.e. they are readily oxidized or reduced “+2” S2O32 thiosulfate +4 SO2 weak LA C2v H2SO3 sulfurous acid SO32- (sulfite) C3v +6 SO3 strong LA D3n H2SO4 sulfuric acid SO42 (sulfate) Td Add BF3 to SO3 to prevent oligomerization

S oxides +6 S2O82 peroxydisulfate S2O82  2 SO4- .  2 SO42- 2e- , ~+2V

Pourbaix diagrams

SN compounds SN compounds (28 pp in Greenwood and Earnshaw, Chemistry of the Elements) S2N2 almost sq. planar S4N4 S4N4  (SN)x polysulfurnitride, zig-zag chain, metallic conduction in chain direction Δ, Ag