# On what factors does "ionization energy" depend?

Aug 9, 2017

On $\text{(i) nuclear charge, Z}$, and.........................$\text{(ii) distance of the valence electron from the nucleus}$

#### Explanation:

And ionization energies clearly indicate a Periodic Trend that manifest the two given properties. Ionization energies INCREASE across the Period, a row, from left to right as we face the Periodic Table, and DECREASE down a Group, a column of the Table.

Now it is a fact that INCOMPLETE electronic shells shield the nuclear VERY INEFFECTIVELY. Consider the following diagram......

And clearly, the LARGEST ionization energy, (which represents the enthalpy change for the following reaction......

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

......occurs for the Noble Gases, which have the highest nuclear charge for a given electronic shell.

A full valence electronic shell, shields the nuclear charge fairly effectively, and thus the alkali metals, with a single valence electron, have demonstrably low ionization energies........