Question

Differentiate between the following terms: Ionisation Energy and Electron Affinity.

Answer 1

The difference between ionization energy and electron affinity is-

Ionization Energy	Electron Affinity
1. It is the minimum energy needed to remove an electron from the isolated gaseous atom to form a cation.	1. It is the energy released when a neutral atom gains an electron to form a stable negative ion.
$$\begin{gathered} \mathrm{Na}+\mathrm{Ionization}\mathrm{enrgy}\to {\mathrm{Na}}^{+}+{\mathrm{e}}^{-} \\ \mathrm{Sodium}\mathrm{Sodium}\mathrm{electron} \\ \mathrm{atom}\mathrm{Cation} \end{gathered}$$	$$\begin{gathered} \mathrm{F}+{\mathrm{e}}^{-}\to {\mathrm{F}}^{-}+\mathrm{Electron}\mathrm{affinity} \\ \mathrm{Fluorine}\mathrm{electron}\mathrm{Fluoride} \\ \mathrm{atom}\mathrm{anion} \end{gathered}$$
2. The amount of ionization energy depends upon the distance of the outer electron from the nucleus and the attractive nucleus pull experienced by the electron	2. Higher the electron affinity, it is easier to add an electron to the valence shell
3. When we move from left to right in a periodic table, the atomic size increases with an increase in the number of protons. Thus, the nucleus attracts the electron more strongly. Hence, Ionization Energy increases from left to right in a periodic table.	3. Electron affinity increases as we from left to right in a period.
4. When we move from top to bottom in a group of a periodic table, a new valence shell is added which increases the distance of the valence electron from the nucleus resulting in lesser attraction between that electron and nucleus. Hence, on moving down a group, the ionization energy decreases.	4. Electron affinity decreases as we move down a group of a periodic table.