Question

Which one of the following is a d-block element?

• A. $Gd$
• B. $Hs$
• C. $Es$
• D. $Cs$

Answer 1

The correct option is B $Hs$

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:

$Gd\left(64\right)=\left[Xe\right]4f^7,5d^1,6s^2$
$Hs\left(108\right)=\left[Rn\right]5f^{14},6d^6,7s^2$
$Es\left(99\right)=\left[Rn\right]5f^{11},7s^2$
$Cs\left(55\right)=\left[Xe\right]6s^1$

Thus, $Hs$ is a d-block element.