Reactivity trends

Question 1

Trend in ionisation energy down a group

Answer 1

Atomic radius increases
Shielding increases
Nuclear charge increases
(but outweighed )
∴nuclear attraction
on outer electron decreases
so less energy needed to remove

Question 2

General trend in ionisation energy across a period

Answer 2

Atomic radius decreases
Shielding stays the same
Nuclear charge increases
∴nuclear attraction
on outer electron increases
so more energy needed to remove

Question 3

Exceptions to general trend in ionisation energy

Answer 3

Be -> B:
B has outer electron
in 2p sub-shell
Be has outer electron
in 2s sub-shell
2p higher energy than 2s
so less energy needed
to remove electron from B

N -> O:
O outer electron paired
N outer electron unpaired
paired electrons experience
greater repulsion
so less energy needed
to remove electron from O