Question

Why does gallium have less atomic radius than aluminum?

Answer 1

Aluminium and gallium belongs to group 13.Generally, atomic radii increases on moving down in a group.But the atomic size of gallium is less than aluminium although it lies below aluminium in the group.This because of the poor shielding effect of electrons in the 3d orbital of gallium.The outermost electrons are poorly shielded.

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Answer 2

Answer:

Gallium has smaller atomic radius than aluminium because the d orbital which is highly diffused offers poor shielding effect which results in increased nuclear charge. Due to increased charge by nucleus, outer electrons get attracted, decreasing the radius.