Evidence for shells in ionisation trends

Ionisation energy is a measure of the ease in which atoms lose electrons and become positive ions.
The first ionisation energy is the energy required to remove one electron from each atom of a mole of gaseous atoms.
M(g) - e^- → M⁺(g)
Further electrons may be removed giving successive i.e.:
M⁺(g) - e^- → M²⁺(g)
This energy is usually quoted in units of kilojoules per mole (kJ mol^-1).
Energy is required to remove an electron from any atom because there is an attractive force between the nucleus and the electron being removed which has to be overcome.
The value of the first ionisation energy depends upon:Shielding involves the repulsion between electrons in inner, filled orbitals and electron being removed from the outer orbital.
An orbital with a single atom in is more stable than one with 2 opposing electrons ! There are trends across the table so the futher up and to the right the greater the ionisation energy excluding group 8/18
and
Ionisation energy is the minimum energy needed to remove a mole of electrons from a mole of gaseous atoms. O has a lower 1st IE than N because O is 1s2 2s2 2p4 and N is 1s2 2s2 2p3. The 4th electron in the O atom's outer level has to pair up with one of the others, and this introduces repulsions, which makes it easier to remove. The relevant factors are nuclear charge, atomic radius and screening by inner electrons.
Hope this helps

So what would the electron orbitals need to look like, in order for it to have a lower ionidation energy (e.g. for oxygen, one example is that the reason why it had a lower IE than nitrogen is because it had half full orbitals)

What other examples are there, like having half full orbitals, are there

Hi Frank

Try this:*http://www.scienceskool.co.uk/ionisation-energies.html

It should answers most of your questions I think.

Alex

I've just taken a quick look at your not-for-profit website. It's extremely good and I would take great please in directing kids towards it. What a generous thing to do!