Group 16

Common oxidation states of Group 16

-2,+4 (not Oxygen),+6 (not Oxygen)

Describe the elemental forms of group 16

• O forms a diatomic molecule with two LP and a double bond

• S has the most naturally occurring allotropes and polymorphs than any other element

• Selenium is similar to sulphur but also contains a metallic form

• Te is a metalloid

• Po is a radioactive metal

State and draw the Sulfur halides that can form

• S2F2

• SF2

• SF4

• SF6

What is notable of SF4

Highly reactive and very toxic releasing HF in the lungs

Describe the notable features of SF6

• Extremely inert being stale up to 500 degrees

• Colourless,Odourless,Tasteless,Non-flammable,Non-toxic

• Very dense at 6.4kg/m³

• Used as an insulating gas in high voltage generators

• No corresponding properties to other Sulphur Hexahalides

• Hypervalence

Describe the hypervalency in SF6 and its formation

• S8 + 24 F2 → 8 SF6

• 6 electrons from sulphur, each fluoride donates 1 electron to S-F bonding, giving it a total 12 valence electrons breaking the octet rules value of 8

• Sulphur contains 4 orbitals for use (3S,3Py,3Px,3Pz) and the 6 Fluorines bonds to sulphur each using a single p orbital, A total of 10 atomic orbitals used in bonding meaning it forms 10 molecular orbitals

• F-Based orbitals combine with Sulphur 3s to give 1 MO, Three more bonding MOs form with 3px, 3py, 3pz. Giving 4 bonding MO.

• Due to sulphur have an opposite phase to its atomic orbitals, we form 4 antibonding MO. So we have 8 total MO

• The final 2 MO come from non-bonding orbitals based entirely on fluorine

Describe bonding in SF6

• Of the 12 electrons 8 occupy bonding MO and 4 occupy non-bonding orbitals.

• Only 8 of the electrons are involved in S-F bonding. Remaining 4 are situated only on fluorine atoms

• SF6 is stable as it has the 4 “extra” electrons placed entirely on the electronegative fluorine atoms.