Urgent: a-level chemistry help

Question: Why does ionisation energy decrease as you go down a group?

Answer: Elements further down a group have extra electron shells. This means they are further away from the nucleus. Meaning that the atomic radius is larger and the energy required to remove an electron decreases.

Hi, I have a question on why the energy required to remove an electron decreases if the electrons are further away from the nucleus. Shouldn't the energy increase as it is harder for the nucleus to remove an electron than if the electrons were more closer. Also, the answer says ' elements down a group have extra electron shell'. Could I say there is an increase in shielding?

hey, yes you can mention about shielding.
For your first question,Think about it like this, as the number of electron shells increase as you go down in the group this means that the hold of nucleus on the electron in the outermost shell decreases. right? Therefore it will be easier to remove that electron in the outermost shell. That is what they mean here by less energy. The thing you misunderstood is that nucleus is removing its own electron, it is talking about the energy required by the neighbouring atom to remove that electron. I hope it helps.