JEE Main · 2021 · 27 Aug 2021 · Shift 1 · d and f Block Elements

The number of

f

electrons in the ground state electronic configuration of

Np (Z = 93)

is ______. (Nearest integer)

Answer: 18

Solution

Neptunium (Np,

Z = 93

) is an actinide. Its ground state electronic configuration is

[Rn] 5 f^{4} 6 d^{1} 7 s^{2}

. However, the question asks for the total number of

f

electrons, which includes both the

4 f

and

5 f

subshells. The

4 f

subshell is completely filled with 14 electrons (from the lanthanide series before radon), and the

5 f

subshell has 4 electrons. Total

f

electrons =

14 + 4 = 18

JEE Main · 2021 · 27 Aug 2021 · Shift 1 · Integer answer