Question

Which one of the following is ${}^{\prime }{d}^{\prime }-$ block element?

• A. Gd
• B. Hs
• C. Es
• D. Cs

Answer 1

Answer: (B)

The element in which last electron enters in $d$-orbital is called $d$-block element.
The electronic configuration of the given elements are as follows
$Gd(64)=[Xe]6s^2,4f^7,5d^1$
$Hs(108)=[Rn]7s^2,5f^{14},6d^6$
$Es(99)=[Rn]7s^2,5f^{11}$
$Cs(55)=[Xe]6s^1$
Thus, $Hs$ is a $d$-block element