• # question_answer Which one of the following is $'d'-$block element?                 A)  Gd             B)  Hs C)  Es              D)  Cs

Correct Answer: B

Solution :

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

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