Question

The atom of which one of the following elements has the highest number of unpaired electrons?

• A. ${}_{25}Mn$
• B. ${}_{24}Cr$
• C. ${}_{96}Cm$
• D. ${}_{26}Fe$

Answer 1

Answer: (C)

The electronic configuration of the given elements is as
${}_{25}Mn=[Ar]3d^5,4s^2$ (Five unpaired electrons)
${}_{24}Cr=[Ar]3d^5,4s^1$ (Six unpaired electrons)
${}_{96}Cm=[Rn]5f^7,6d^1,7s^2$ (Eight unpaired electrons)
${}_{26}Fe=[Ar]3d^6,4s^2$ (Four unpaired electrons)
Thus, ${}_{96}Cm$ has the highest number of unpaired electrons.