Trends of Period 3 Elements: First Ionisation Energy

Question 1

The first ionisation energy (IE1) is the

Answer 1

energy required to remove one mole of electrons from one mole of atoms of an element in the gaseous state to form one mole of gaseous ions

Eg. the first ionisation energy of Na is:
Na (g) → Na+ (g) + e-

Question 2

There is a general increase in IE1 across a period as

Answer 2

The nuclear charge increases

The atomic radius decreases

There are stronger attractive forces between the nucleus and outer electrons

It therefore gets harder to remove any electrons

Small ‘dips’ are observed between Mg - Al and P - S