14.1 Further covalent bonding and structure

Question 1

Explain expanded octet rule

Answer 1

Expanded octet is when an atom holds more than 8 e in the outer shell - possible for period 3 and below (d block - similar E to p - accessible for e) - orbital splitting

Expansion from 3p to 3d - allows more bonding pairs to form

Question 2

What is formal charge and how to calculate it?

Answer 2

Formal charge: allows to deterine which is the most stable structure

FC = (# valence e in free atom) - 0.5 (# bonding e) - (# non bonding e)

FC = V - 0.5B - L

FC wants to be as close to 0 as possible -

Question 3

Atmosphere anatomy

Answer 3

Ozone layer

Question 4

Function of ozone layer

Answer 4

Protect the Earth from harmful UV radiation - absorbs UV-B, UV-C - damage to living tissues

Also absorption creates necessary heat - determines Earth’s temperature

Question 5

How is ozone layer maintained?

Answer 5

Ozone maintained by formation and breakdown of oxygen and ozone

Question 6

How is ozone layer destructed?

Answer 6

Ozone absorbs UV - reactive - reacts with human released nitrogen oxides NO_x (vehicle engines) and chlorofluorocarbons (CFC) (aerosols, refrigerants, solvents) - produce highly reactive free radicals decomposition of ozone to oxygen

Question 7

Explain sigma bond

Answer 7

Sigma bond: two atomic orbitals overalp by the ends (s, p, hybrid), density is concentrated between nuclei

Question 8

Explain pi bonds

Answer 8

Pi bonds: two orbitals overlap sideways, concentrated in two regions: above and below bond axis, forms only alongside sigma bonds, weaker than sigma - e density further from nucleus