# Question #ece52

Jul 15, 2017

The ionization energy is the energy it an atom must absorb (hence, the positive sign, usually) to lose an electron.

Ionization energy generally increases left to right and down to up. This is due mainly to the effective nuclear charge of the atoms. There are some anomalies, but for the most part one can rely on this trend.

Here, we're considering one atom and an ion: $P$ and ${N}^{-}$.

$P$ is below, and further left to ${N}^{-}$, thus:

${P}_{I} < {N}_{I}^{-}$

More specifically, if we look these up:
${P}_{I 1} = \frac{1101.8 k J}{m o l}$, ${N}_{I 1}^{-} = \frac{1314 - 1400 k J}{m o l}$

Note: the ${N}^{-}$ ionization energy is a range of nitrogen and oxygen's, since an ion, and hence, has as many electrons as oxygen, but a lesser effective nuclear charge.