Periodicity of Ionisation Energy

What happens as you move across a period?

The ionisation energies increase and it gets harder to remove the outer electrons.

Why do the ionisation energies increase as you go across a period?

The number of protons is increasing, which means a higher nuclear charge, so a smaller atomic radius and a stronger attraction.

Where are all the extra electrons at?

Roughly the same energy level, even if the outer electrons are in different orbital types.

What do the extra electrons at roughly same energy level mean?

There's generally little extra shielding effect to lessen the attraction from the nucleus

What happens to the ionisation energies across the period?

It increases yet not always, as there are small drops between groups 2 and 3, and 5 and 6.

What's the drop between groups 2 and 3 due to?

The outer electrons in group 3 elements being in a p-orbital rather than an s-orbital

What's the drop between groups 5 and 6 due to?

Electron repulsion