Question

What is the order of ionization enthalpy for $\mathrm{B},\mathrm{Al},\mathrm{and}\mathrm{Ga}$?

Answer 1

Ionization enthalpy:

• “A quantitative measure of the tendency of an element to lose electron is given by its Ionization Enthalpy.”
• “It is the energy required to remove an electron from an isolated gaseous atom $\left(\mathrm{X}\right)$ in its ground state.”
• The first ionization enthalpy for an element $\mathrm{X}$ can be depicted as:

$\mathrm{X}\left(\mathrm{g}\right)\to \mathrm{X}+\left(\mathrm{g}\right)+{\mathrm{e}}^{-}$

• The unit of ionization enthalpy is $\mathrm{kJ}{\mathrm{mol}}^{-1}$.

Trends of ionization enthalpy in Group-$13$:

• The trend in ionization enthalpy is because there is a decrease in Ionisation enthalpy from $\mathrm{B}$ to $\mathrm{Al}$ due to an increase in size and from $\mathrm{Al}$ to $\mathrm{Ga}$.
• $\mathrm{Ga}$ has more ionization energy than $\mathrm{Al}$ due to the uneffective screening effect.
• Hence, the trend is as follows:

$\mathrm{B}>\mathrm{Al}<\mathrm{Ga}$