G16 (Chalcogens)
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What is the trend in G16 for catenation
- S and Se have tendency to catenate
(to form chains of atoms of the same
element)
- Te is however too metallic to catenate
(i.e it lacks covalent component of bond-
ing) to catenate.
What is the trend in metallic character in
G16
- As you go down G16, metallic character
increases going down the group.
- O and S are non-metals
Se and Te are metalloids.
- Po is a metal
What is the trend of coordination num-
bers
- O achieves lower max CN than other
G16 elements.
- Max CN is 3 this is because of a small O
atom size combined with extremely high
electronegativity.
What is the trend with the rise of al-
lotropes?
- In G16 O amongst elements form par-
ticularly strong À bonds with themselves
and with each other.
- This gives rise to allotropes and com-
pounds with multiple bonds i.e O2 and
O3 this is denied to heavier elements.
What is the influence of the inert pair
effect in G16? S is less oxidising than Se or Te
What are the 2 natural allotropes of Oxy-
gen
Dioxygen O2 - Biradical with triplet
ground state therefore:
1. Reactive in gas phase
2. Colourless in liquid phase
3. Pale blue colour in solid state
Ozone O3
- Unstable, very strong oxidising agent.
Diamagnetic, bent structure, pale blue
even in gas phase
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