Periodic trends - ionisation energy

Question 1

Definition of ionisation energy

Answer 1

The energy required to remove one mole of electrons from one mole of atoms in the gaseous state

Question 2

Are ionisation energies endothermic or exothermic

Answer 2

Endothermic- they take in energy from the surroundings to remove the electrons

Question 3

General equation for first ionisation energy

Answer 3

E(g) —> E+(g) + e-

Question 4

General equation for second ionisation energy

Answer 4

E(g) —> E2+ (g) + 2e-

Question 5

Ionisation energy….across a period

Answer 5

Increases

Question 6

Explanation for ionisation energy ……across a period

Answer 6

It increases going across a period as the nuclear charge is increasing. Therefore there is a greater force of attraction between the outer electrons and the nucleus, meaning they will be held together more strongly - leading to a increase in energy required to remove them

Question 7

Ionisation energy …. going down a group

Answer 7

Decreases

Question 8

Explanation for why ionisation energy …. going down a group

Answer 8

Ionisation energy decreases going down a group as there are more electron shells between the nucleus and the electron being removed (the electron will be further from the nuclear charge making the force between them weaker). The inner electron shells will also shield the outer electrons from the attraction of the larger nuclear charge, decreasing the force of attraction between them therefore making it easier to remove the outermost electron