How would you explain lower atomic radius of Ga as compared to Al ?

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p-Block Elements - I

easy

How would you explain the lower atomic radius of $Ga$ as compared to $Al$?

Option A

Option B

Option C

Option D

Solution

Atomic radius (in $pm$)
Aluminium	$143$
Gallium	$135$

Although $Ga$ has one shell more than $A l$ its size is lesser than $A l$ . This is because of the poor shielding effect of the $3 d -$ electrons. The shielding effect of $d -$ electrons is very poor and the effective nuclear charge experienced by the valence electrons in gallium is much more than it is in the case of $Al$

Standard 11

Chemistry