Question

In an iron atom $(\mathrm{Z}=26)$, the differentiating electron enters which of the following sublevel.

• A. $3\mathrm{d}$
• B. $4\mathrm{d}$
• C. $4\mathrm{p}$
• D. $5\mathrm{p}$

Answer 1

The correct option is A

$3\mathrm{d}$

Explanation:

Differentiating Electrons:

• In transition metal, the differentiating electrons go through the penultimate shell.
• The penultimate shell is that the shell immediately presents previous to the valence or the last shell. i.e., the second last shell of the atom.
• Iron$\left(\mathrm{Fe}\right)$ is a transition metal and its atomic number is $26$.
• So, the electronic configuration of Iron is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^{6}4{\mathrm{s}}^2$.
• So, the differentiating electron of iron enters in $3\mathrm{d}$ subshell.

Hence, option (A) is the correct answer. In an iron atom $\left(\mathrm{Fe}\right)$, the differentiating electron enters the subshell $3\mathrm{d}$.