Ionisation Energies

Question 1

What is an ionisation energy

Answer 1

The amount of energy needed to remove one mole of electrons from one mole of gaseous atoms

Question 2

Explain the trend in first I.E. down the group

Answer 2

1st IE decreases because there is increased shielding and the electron is further from the nucleus meaning there is less effective charge

Question 3

Trends in IE across a period

Answer 3

1st IE increases across a period because the charge on the nucleus increases left to right, but there is no extra shielding to compensate. Therefore the effective charge increases and it is harder to remove the electron

Question 4

Why are Boron and Aluminium exceptions to the first IE rule

Answer 4

They have an extra orbital beneath them (3s) and so they have increased shielding as opposed to Beryllium and Magesium

Question 5

Why do Oxygen and sulphur have lower 1st IEs than nitrogen and phosphorus

Answer 5

Oxygen and sulphur have paired electrons in their outer energy level which naturally repel each other making them easier to remove

Question 6

Why is there a large jump found at some point in successive IEs

Answer 6

It is where the electron being removed is from the next energy level in and so there is less shielding and it is harder to remove