Question

The atomic sizes of $Ga$ and $Al$ are almost same because

• A. Poor shielding effect of the electrons in $d$ orbitals,effective nuclear charge increases in gallium.
• B. More shielding effect of $d$ electrons
• C. Poor shielding effect of $f$ orbitals in gallium
• D. High screening effect of $3s,3pand3d$ electrons.

Answer 1

The correct option is A Poor shielding effect of the electrons in $d$ orbitals,effective nuclear charge increases in gallium.

Due to the poor shielding effect of $d$-electrons,the screening effect (or shielding effect) decreases for the outermost electrons. As a result,the effective nuclear charge on the outer electrons increases, which results in decrease in its size. Hence, $GaandAl$ are almost same in size.