Question

Electronic configuration of a transition element X in +3 oxidation state is [Ar]3d⁵. The atomic number is .

• A. 27
• B. 26
• C. 24
• D. 25

Answer 1

The correct option is B 26

Firstly , the atomic number of Ar is 18, 5 is then added to 18 due to presence of electrons in $d-orbital$. Total number of electrons in $X^{+3}$ is 23.
Oxidation means loss of electrons , so, +3 charge implies 3 electrons loss by X to form $X^{+3}$.
Hence , number of electrons in
X = 23 + 3 = 26.
We know that in a neutral element, number of electrons = number of protons = atomic number.
Therefore, atomic number of X = 26