the main group elements sulfur selenium tellurium and polotinum n.
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The Main Group Elements Sulfur, Selenium, Tellurium, and Polotinum. Group Tendency (p230). Lower electronegativities: less ionic character Character of multiple bonding for sulfur: d π -p π bonding, litlle if any p π -p π such as S─O in SO 4 2– Valence: not confined to 2, more to 4

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group tendency p230
Group Tendency (p230)
  • Lower electronegativities: less ionic character
  • Character of multiple bonding for sulfur: dπ-pπ bonding, litlle if any pπ-pπ

such as S─O in SO42–

  • Valence: not confined to 2, more to 4

such as SF6, and Te(OH)6

  • Tendency catenation for sulfur: equaled tor exceeding only by carbon Sn 2–

For O, Se and Te, weaker in this tendency

group tendency p2301
Group Tendency (p230)
  • The increasing size of the atoms and the decreasing electronegativity on going from S to Po are responsible for the changes in the properties of the elments. The examples as:
  • The decreasing stability of H2E
  • The increasing tendency to for complex ions SeBr62–
  • The metallic properties for Te and Po

MO2 are ionic and basic, reacting with HCl to give the chlorides

key information p231
Key Information (p231)
  • Name: Sulphur or Sulfur
  • Symbol: S
  • Atomic Number: 16
  • Atomic Weight: 32.065amu
  • Group Number: 16
slide5
Group Name: Chalcogen
  • Block: p-block
  • Standard State: Solid at 298K
  • Color: Bright yellow
  • Classification: Non-metallic
the history of sulfur
The History of Sulfur
  • Sulfur dates back as far as ancient times.
  • It Genesis it was referred to as brimstone, and in 700-600 BC the Assyrian texts called it the “product of the riverside.”
  • It is thought that the Chinese discovered gun powder around the 12th century.
slide7
The person that should be credited with convincing the scientific community that sulfur was an element around 1777 is Antoine Lavoisier.
  • Sulfur is also know as one of the elements that has an alchemical symbol.
isolation
Isolation
  • Sulfur is readily available, so it is not necessary to make it.
  • It is a native element in nature and can be extracted by the Frasch process.
  • This process requires superheated water and steam to melt the sulfur. Commercial success for this process depends on ideal geological conditions.
slide10
Hydrogen Sulfide, H2S, is a main impurity in natural gas and it must be removed before the gas can be used.
  • It is removed by absorption and regeneration followed by a catalytic oxidation using porous catalysts like Al2O3 or Fe2O3 (Claus process).
    • 8H2S + 4O2 —> S8 + 8H2O
additional properties
Additional Properties
  • Melting Point: 112.8°C
  • Boiling Point: 444.6°C
  • Density at 293K: 2.07 g/cm3
  • Crystal Structure: Orthorhombic
  • S8 and S∞
reactions
Reactions
  • Sulfur burns in air to form dioxide sulfur(IV)oxide.
  • S8(s) + 8O2(g) —> 8SO2(s)
  • Sulfur reacts with all halogens upon heating.
  • S8 + 4Cl2 —> 4S2Cl2(l)
  • S2Cl2(l) + Cl2 <=> 2SCL2(l)
slide13
Sulfur also reacts with bases.
  • S8(s) + 6KOH(aq) —> 2K2S3 + K2S2O3 + 3H2O(l)
  • Sulfur also reacts with Lewis Acids
  • S8(s) + 3SbF5 S82+ + 2SbF6– + SbF3
key information
Key Information
  • Name: Selenium
  • Symbol: Se
  • Atomic Number: 34
  • Atomic Weight: 78.96amu
  • Group Number: 16
slide15
Group Name: Chalcogen
  • Block: p-block
  • Standard State: Solid at 298K
  • Color: Grey, Metallic lustre
  • Classification: Non-metallic
the history of selenium
The History of Selenium
  • Selenium was discovered in 1817, by Jons Jacob Berzelius.
  • He originally reported the impurity in sulphuric acid to be tellurium, but latter found that is was selenium instead of tellurium.
isolation1
Isolation
  • Selenium is an element that is readily available, so it is not necessary to make it.
  • Most selenium is made as a byproduct of copper refining.
  • It also accumulates in the residues from sulphuric acid manufacture.
slide18
Extraction is a two step process:
  • Cu2Se +Na2CO3 + 2O2—> 2CuO + Na2SeO3 + CO2
  • The selnite is acidified with sulphuris acid
  • H2SeO3 + 2SO2 + H2O —> Se + 2H2SO4
additional properties1
Additional Properties
  • Melting Point: 217.0°C
  • Boiling Point: 684.9°C
  • Density at 293K: 4.79 g/cm3
  • Crystal Structure: Hexagonal
reactions1
Reactions
  • Selenium reacts with air:
  • Se8(s) + 8O2—> 8SeO2(s)
  • Selenium reacts with halogens:
  • Se8(s) + 16F2(g) —> 8SeF4(s)
  • Se8(s) + 16Cl2(g) —> 8SeCl4(s)
  • Se8(s) + 16Br2(g) —> 8SeBr4(s)
  • Se8(s) + 16I4(s) —> 8SeI4(s)
hydrides eh 2 p232
Hydrides EH2 (p232)
  • Preparation:
  • M2E + H+ H2E
  • MeC(S)NH2 + 2H2O H2S
  • Toxicity: H2S Far exceeds that of
  • HCN
  • Thermal Stability and bond strength: decrease down the series Why ?
  • Acidity in water : increase Why ?
  • Reducity: H2Sx Sulphane, Polysulfide
  • Na2S5, K2S6 and BaS4 as ligand
metal sulfides
Metal Sulfides
  • Na2S and BaS dissolve in water
  • Cr2S3 and Al2S3 hydrolysis fully
  • MnS and ZnS dis. dilute HCl
  • CdS Concentric HCl
  • CuS HNO3
  • HgS HNO3 + HCl
  • Note: Ksp and Complex; Color
slide24

Halides of Group 16

Sulphur, selenium and tellurium have extensive halogen chemistries.

S forms stable compounds with F, Cl, Br

unstable compounds with I

Se and Te form stable compounds with all halogens

slide27

S8 + 24F2 8SF6

Fluorine brings out the highest oxidation states

SF6, SeF6 andTeF6 are all stable compounds

slide28

There are some REALLY interesting in its structures with fluorine

S2F10

FSSF, FSeSeF?

SSF2, SeSeF2?

SF2, SeF2

S2F4

SF4, SeF4

TeF4

slide29

The structures of the fluorides are all readily modeled by VSEPR

SF4 (10 valence electrons) is therefore trigonal bipyramidal with L.P. in axial position

NOT tetrahedral!

Where asymmetry exists in the S-F structures, compounds are reactive, when symmetric, unreactive

  • SF4 – highly reactive gas
  • SF6 – very unreactive
  • -used to blanket electrical transformers
  • -S-F bond remains reactive, reactions kinetically
      • hindered

Less sterically crowded Se and Te hexafluorides are more

reactive.

slide30

Te2Cl

SCl2, SeCl2, TeCl2

S2Cl2, Se2Cl2

S3Cl2, Se3Cl2

SCl4, [SeCl4]4, [TeCl4 ]4

Te2Br

SeBr

SeBr2, TeBr2

S2Br2, Se2Br2

[SeBr4]4, [TeBr4 ]4

Lower halides

slide31

Te2I

TeI

Te4I4

S2I2,

[TeI4 ]4

slide32

Just because a compound isn’t stable, doesn’t mean that folks won’t try to make something like it:

S – I compounds: Only S2I2 known and it is quite reactive

[S7I]+[AsF6]-

[S2I4]2+[AsF6-]2

[SeI3+][AsF6-]

[TeI3+][AsF6-]

[SeBr3+][AsF6-]

[TeBr3+][AsF6-]

[SBr3+][AsF6-]

sulfur oxo chlorides p234
Sulfur Oxo-chlorides (p234)
  • Thionyl chloride (SOCl2)
  • SO2 + PCl5 SOCl2 + POCl3
  • SOCl2 + 2H2O SO2 + 2HCl
  • Used as dehydratant to prepare anhydrous chlorides
  • Sulfuryl Chlride (SO2Cl2)
  • SO2 + Cl2 SO2Cl2
  • Both can react with ammonia
oxides so 2
Oxides: SO2
  • AB2E SP2
  • V-shape
  • Lewis base: S / O donar atom
  • Lewis acid: π* orbital
  • Solubility in water: good
  • SO2 + xH2O SO2 ·xH2O (gas hydrate) HSO3–
  • K = 1.3E-2

..

..

..

..

..

slide36
SO3
  • Preparation: SO2 react with O2, catalyzed by Platinum sponge, V2O5, NO
  • Structure: planar (g); cycle or polymer (s)
  • Solubility in water: easy, giving H2SO4
slide37

SeO2 is exclusively polymeric (consistent with move to more polar/ionic character as group is descended). Linear zig-zag structure.

SeO3 is a cyclotetramer (cf SO3).

suluric selenic and telluric acids p238
Suluric, Selenic and Telluric acids (p238)
  • Acidic anhydrides: AO3
  • Preparation: H2SO4,SO3 absorbed in concentrated H2SO4; Te(OH)6, oxidation of TeO2 by H2O2 Why ?
  • Strong dehydratant: H2SO4 and H2SeO4
  • Strong oxidizing agents: H2SO4 < H2SeO4Why ?
  • The isomorphism of salts:

MI2SO4 ·MIISO4·6H2O

MI2SO4 ·M2III(SO4)3·24H2O

  • Solubility of salts in water: good (ionic character) but…
thiosulfates p238
Thiosulfates (p238)
  • Preparation:

SO32- + S S2O32- S + SO2

  • To be easily oxidized

S2O32- + I2S4O62-

Cl2 SO42-

  • As ligand (used in photography)

[Ag(S2O3)]- [Ag(S2O3)2]3-

AgS + SO42-

Δ

H+

S

S

O

O

O

H2O

dithionites
Dithionites
  • Sulfite SO32- + I2HSO4-

S2O42-

  • Na2S2O4 strong reductant

Dithionates

  • MnO2 + 2SO32- + 4H+ Mn2+ + S2O62- + 2H2O
  • S4O62-

SO2, Zn

O

O

S

S

O

O

O

O

peroxodisulfate
Peroxodisulfate

2HSO4- - 2e– S2O82- + 2H+

8H2O + Mn2+ + S2O82-MnO4- + 2SO42- + 16H+

Ag2+

Ag+

disulphurate
Disulphurate
  • H2SO4 + SO3 H2S2O7
  • 2KHSO4K2S2O7 + H2O
  • K2S2O7 + Ai2O3Al2(SO4)3 + K2SO4

Δ

Δ

Δ