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

1.	How would you explain the lower atomic radius of Ga as compared to Al ?
Answer» Solution :Although Ga has one shell more than Al, its size is LESSER than Al. This is because of the poorshielding EFFECT of the 3d-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.

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