# How do 1st, 2nd and 3rd ionisation energies compare in metals, non-metals and noble gases?

Jun 28, 2017

Well, we would expect them to increase in the order of successive ionizations............$\text{1st ionization energy"<"2nd ionization energy} < \ldots$

#### Explanation:

And we would also expect them to increase in the order...... $\text{metals}$ $<$ $\text{non-metals}$ $<$ $\text{Noble Gases}$.

So why?

Metals are generally regarded as electron-rich materials, whose valence electrons are delocalized and should thus be more or less easily removed from the individual metal atom.

And thus the ionization reaction.......

$M \left(g\right) + \Delta \rightarrow M {\left(g\right)}^{+} + {e}^{-}$

.......should have relatively small values of $\Delta$. As we look at successive ionization energies, electrostatics alone would suggest that the 2nd and 3rd ionization energies should be intrinsically HIGHER, inasmuch it is harder to oxidize a positive ion or a dipositive ion than a neutral atom.

On the other hand, non-metals are oxidizing materials, which tend to accept electron density. Their nuclear charge, and incomplete valence shell, thus means they tend to be oxidized. Their ionization energies, first, second, etc. should thus be intrinsically high.

And on the other, other hand, the Noble Gases have a complete valence shell; i.e. electronically stable. These should possess the highest ionization energies.

Anyway, as a chemist, as a physical scientist, you should inform your argument with data. Take a look at the successive ionization energies of the elements, and see if their values are consistent with what we have argued here.