Question

- Give reasons for the following
(i)The size of Ga is smaller than Al.

Answer 1

In morden periodic table, atomic radius increases when we go downwards a group, and if you will see the periodic table, aluminium comes first and gallium in its next period.

The reason behind this property is simple, as when we move down a period, no. of power shell increases gradually, like in first period, only k-shell is present, and in second, only k and l-shells are present.

But, although gallium lies next to aluminium in the group, gallium is smaller then aluminum because galliam electrons occupy 3d sub shell hence resulting in reduction of affective nuclear charge. This happens because of the difference in attraction forces of electrons on nucleus. This is also called shielding affect.

So when atrraction force is big between electrons and protons, it results in shrinking of atom hence reducing its radius.

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Answer 2

Answer:

Due to the poor screening the radius of Gallium(Ga) is lesser than Aluminium (Al) because in going from Al to Ga, the electrons have already occupied 3d sub shell in Ga. Hence Ga is smaller than Al.

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