Gallium lies below aluminium in group 13 of the periodictablebut itsatomicradiusis smallerthan that ofaluminium. Why so ?

Gallium lies below aluminium in group 13 of the periodictablebut itsat

1.	Gallium lies below aluminium in group 13 of the periodictablebut itsatomicradiusis smallerthan that ofaluminium. Why so ?
Answer» Solution :DUE to poorshielding of the valenceelectrons of GABY the inner 3d-electrons , the effectivenuclearcharge of GA is greaterin magnitudethan that of AL. As a result , the electronin gallium experience greaterforce of attractionby the NUCLEUS than in Aland hence atomic size of Ga (135pm)is slightly lessmuch higher than that of Al (143pm).