There is a sharp decrease in the ionisation energies from boron to aluminium but it is almost the same from aluminium to gallium. Justify.

There is a sharp decrease in the ionisation energies from boron to al

1.	There is a sharp decrease in the ionisation energies from boron to aluminium but it is almost the same from aluminium to gallium. Justify.
Answer» Solution :Among IIIA group elements, boron has the highest ionisation POTENTIAL due to smaller size. The SHARP decrease in ionisationenergy from boron to aluminium is due to increase in atomic radius. The atomic radius INCREASES due to decrease in effective NUCLEAR charge. In gallium contraction in atomic size is significant due to the presence of completely filled d-electrons in the penultimate shell. Thus. The effective nuclear charge increases. Hence, both aluminium and gallium have almost equal ionisation energy values.