Explain Why Lithium, Sodium And Potassium Have First Ionisation Energies That Are Lower Than The Elements With An Atomic Number One Above Or One Below It.

[sophiesmithers98]

This is for an AS LEVEL question so I'm guessing for 2-4marks? Please help me.
Thanks

[Buenchico]

This explains it. (I've tried to think of a way of summarising it but it's probably easier if you read it for yourself - start at "Explaining the pattern in the first few elements"):
http://www.chemguide.co.uk/atoms/properties/ies.html

[mibn2cweus]

^ ★★★★★ ^

[Peter Pedant]

thanks Chris

I kinda need to lie down after reading that !

I liked the discussion on the d orbitals filling first in the transition series, but then the s electrons ionise first

[Dodger666]

Do they tell you the questions before the exam these days?

[factor-fiction]

Past papers are available, Dodger, and it's a good idea to work through them and ask for help if you're stuck