Question

Identify the incorrect statement (s) among the folllowing:

• A. If there were three possible values for spin quantum number, then 4th period of periodic table would have maximum of 27 elements.
• B. Platinum ($Pt$) is one of the typical transition metal.
• C. Total number of $f-$ electrons in $Gd$ (at No. 64) is 8.
• D. Atomic number of $Ga$ is nearly equal to that of $Al$

Answer 1

The correct option is C Total number of $f-$ electrons in $Gd$ (at No. 64) is 8.

(A) Three possible spin quantum number means an orbital can have at the most three electrons. So 4th period involves, $4s,3d$ and $4p$ subshells.
So, maximum of electrons (and hence elements)$=4s^{3}3d^{15}4p^9=3+15+9=27$
(B) All elements of VIII the group (i.e., 8, 9, 10 groups) are called typical transition metals. $Pt$ also belongs to 10th group. So it is a typical transition metal.
(C) E.C. of $Gd\left(64\right)=\left[Xe\right]4t^{7}5d^{1}6s^2$
So number of $f-$ electrons = 7
(D) Due to ineffective shielding by $3d-$ electrons in $Ga$, size of $Ga$ is smaller (almost equal) to that of $Al$
Hence (C) is correct.