7.2 Ionisation Energy

1st Ionisation energy

The energy required to remove 1 mole of electron from 1 mole of a gaseous element

2nd Ionisation energy

The energy required to remove 1 mol of electron from 1 mol of a gaseous ion to form 1 mol of a gaseous 2+ ion

What affects ionisation energy

Atomic radius

Electron shielding

Nuclear attraction

( if outermost electron is easier to lose I.E decreases, if outermost electron is harder to lose I.E increases)

Why is the 2nd Ionisation energy greater than 1st

Nuclear attraction increases

More energy is required to remove another electron

How to identify an element from its successive ionisation energies (period of element is given)

Identify where the biggest difference is (e.g between the 3rd and 4th I.E)

Therefore the group of the element will be the 3rd

Locate the element that lies in the given period within the 3rd group

Explain which element has the higher/lower I.E and why

Boron has a lower I.E because it has an unpaired electron in the 2p sub shell which has a higher energy than electrons in the 2s sub shell. This means that it is easier to remove that electron from Boron than it is from Beryllium

Explain which element has the higher/lower I.E and why

Both Nitrogen and Oxygen have the highest energy electrons in the 2p sub shell

In oxygen there is an orbital with a paired electron that repel, making it easier to an electron in comparison to Nitrogen meaning that Oxygen has a lower I.E