Chapter 16
Group 16 Elements
Physical Properties
The elements
Halides, oxohalides, oxides, salts of oxoacids
Metal sulfides, polysulfides, polyselenides,
polytellurides
Compounds of sulfur and selenium with nitrogen
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Dioxygen makes up 21% of the
Earth’s atmosphere and 47% of
the Earth’s crust is composed of
O-containing compounds (water,
limestone, silica, silicates).
Sulfur occurs around volcanoes
and hot springs, iron pyrites
fool’s gold (FeS2), and other
minerals.
Selenium and Tellurium are
relatively rare and occur in only
a few minerals
Polonium is omitted because its
abundance is only 3 × 10−7 ppb,
giving a negative number on the
log scale.
Relative abundances of the group
16 elements in the Earth’s crust
Production of sulfur in the US from 1980 to 2008
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Uses of sulfur and sulfuric acid
3
Given the ∆fHo(Na2O,s) = -414 kJ/mol, determine the
enthalpy change for the process: 2Na+(g) + O2-(g)
Na2O(s)
Hint: Create an appropriate Born-Haber cycle and look up the
necessary values for each of the steps.
2Na (s) + ½ O2(g)
2∆aHo(Na)
∆aHo(O)
∆fHo(Na2O,s)
Na2O (s)
2Na (g) + O (g)
2 IE1(Na)
∆latticeHo(Na2O,s)
∆EAHo1(O)
∆EAHo2(O)
2Na+ (g) + O2-(g)
4
Chemistry of oxygen
MnO2 or Pt catalyst
2H2O2
2KClO3
∆, MnO2 catalyst
O2 + 2H2O
3O2 + 2KCl
Describe bonding in [O2]+, O2, [O2]-, [O2]2- using MO theory.
O2 + PtF6
[O2]+[PtF6]-
2O2F2 + 2BF3
2[O2]+[BF4]- + F2
Chemistry of ozone and ozonide
3/2 O2(g) → O3(g)
∆fHo(O3,g,298 K) = +142.7 kJ mol-1
O3(g) + 2H+(g) + 2e- ⇌ O2(g) + H2O(l)
Eo = +2.07 V
The structures of O3 and [O3]−, and contributing resonance structures in O3.
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The O−O bond order in O3 is taken to be 3/2.
2KOH + 5O3
2KO3 + 5O2 + H2O
(Ozonide salts)
Phosphite ozonide
5
Sulfur: allotropes
S6
S7
S8
catena-S
S8 + 24F2 → 8SF6
S8 + 4Cl2 → 4S2Cl2
S8 + 4Br2 → 4S2Br2
SF6
structure of [S2I4]2+
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Polysulfides, [Sx]2-, and polythionates are formed from reaction of sulfur
with hot aqueous alkali
polythionate
Vulcanization – soft rubber is toughened by cross-linking polyisoprene
chains. Hydrocarbons are dehydrogenated when heated with sulfur and
further reaction with alkenes occur.
Other reactions of sulfur:
1/8 S8 + CO
O=C=S
1/8 S8 + CN-
Na2SO3 + 1/8S8 –H2O, 373 K
S8 + 3AsF5 –liquid SO2
N=C=S- ⇌ NΞC-S-
Na2S2O3
[S8][AsF6]2 + AsF3
[S8]2+ is red and undergoes a change in ring conformation…
[S8]2+
7
[S19]2+
S82+
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transannular interactions
Cross ring S-S separations
smaller than the sum of van
der Waals radii
Delocalized bonding
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Two 7-membered, puckered rings
connected by a 5-atom chain
Charge localized on the threecoordinate S
Selenium
4SeCl2 + 4Ph3PSe
Se8 + 4Ph3PCl2
Inorganic Chemistry By Egon Wiberg, Nils Wiberg, Arnold Frederick Holleman
8
tellurium
4+
2ReCl4 + 15Te + TeCl4 –heat in sealed tube→ 2[Te8][ReCl6]
BaO2 + H2SO4 → BaSO4 + H2O2
Production of H2O2
2[NH4][HSO4] – electrolytic oxidation, “-H2”
[NH4]2[S2O8]
2[NH4][HSO4] + H2O2
H2O2 stabilizer
catalytic cycle used in the industrial
manufacture of hydrogen peroxide
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H2O2
H2O2
H2O2 + 2H+ + 2e- ⇌ 2H2O
O2 + 2H+ + 2e- ⇌ H2O2
Eo = +1.78 V
Eo = +0.70 V
Cl2 + H2O2 → 2HCl + O2
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Peroxo complexes
[V(O2)2(O)(bpy)]−
[Mo2(O2)4(O)2(µ-OOH)2]2−
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Polysulfanes: H2SX
n=2
2H2S + SnnCl2
H2Sn+2 + 2HCl
Polysulfides: [SX]2-
[S6]2-
[AuS9]2-
[Zn(S4)2]2-
[Mn(S5)(S6)]2-
[(S6)Cu(µ-S8)-Cu(S6)]4-
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Polyselenides and polytellurides: [Sex]2- and [Tex]2DMF*
3Se + K2Se2
K2[Se5]
*DMF = Dimethylformamide =
4Se + K2Se2 + 2[Ph4P]Br
DMF, 15-crown-5
3 Se + K2Se2
2K + 3 Te
O
F
[K(15-crown-5)]2[Se5]
1,2-diaminoethane, crypt-222
[Te5]2-
103°
[Ph4P]2[Se6] + 2KBr
[K(crypt-222)]2[Te3]
[Te8]2-
141 pm
F
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Sulfur fluorides and oxofluorides
S2F10
SOF2
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Sulfur chlorides and oxochlorides
1/4S8(l) + Cl2(g) -
S2Cl2
206 pm
193 pm
Reaction Chemistry S2Cl2
2SO2 + S2Cl2 + 3Cl2
SO3 + SCl2
2SCl2 
4SOCl2
SOCl2 + SO2
S2Cl2 + Cl2
Cl-S-S
108°
Internal dihedral angle = 84°
Reaction Chemistry of
SOCl2
RCO2H + SOCl2
RC(O)Cl + SO2 + HCl
SOCl2
SO2Cl2
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SeF4
TeF4
Se4Cl16
Tellurium halides
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MO diagram for octahedral [ECl6]2− (E = Se or Te)
Oxides of Sulfur
SOCl2 + Ag2S -430 K
S2O + 2AgCl
HS7H + SOCl2 → S8O
S8 ----CF3C(O)OOH → S8O
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[SO2N3]-
[(SO2)3N3]-
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Gas phase form of SO3 also
exists as a trimer of SO4 units.
Solid state form exists
as polymeric chains
Oxides of selenium and tellurium
[Te3O6F3]3-
SeO3 tetramer
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Oxoacids and their salts: S
H2S + HSO3Cl -low temp-
H2O2
ClSO3H
-HCl
H2SO5
ClSO3H
-HCl
H2S2O3 + HCl
H2S2O8
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[S2O6]2−
H2SO4 (g)
H2SO4 (l)
Sulfur-Nitrogen Compounds
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Potential diagrams (values in V) for sulfur, selenium and tellurium at
pH = 0.
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