Unit 1: Ionisation energy

Question 1

What’s the first ionisation energy?

Answer 1

The energy required to remove one mole of electrons from one mole of GASEOUS atoms.

Question 2

Is ionisation exo or endothermic?

Answer 2

Endo as it requres energy

Question 3

What happens to ionisation energy across a period?

Answer 3

It increases.

Question 4

What happens to I.E down a group?

Answer 4

It decreases.

Question 5

Why is second or third I.E sometimes significantly higher?

Answer 5

It may be due to pulling from a full shell which is stable and harder to break an electron from causing a significantly higher I.E.

Question 6

Why does I.E increase across a period?

Answer 6

As the atomic number increases the number of protons increase.
More protons = stronger nuclear charge.
Stronger charge = tighter attraction.
Tighter attraction = harder to break electrons from shells.
Harder to break = higher ionisation energy.

Question 7

Why does I.E decrease down a group?

Answer 7

There are more full shells.
Full shell = more shielding.
More shielding = less attraction between electron and nucleus.
Less attraction = easier to pull electron.
Easier pull = lower ionisation energy