Question

Electronic configuration of a transition element 'X' in +3 oxidation state is $\left[Ar\right]3d^5$. What is its atomic number?

• A. 25
• B. 26
• C. 24
• D. 27

Answer 1

The correct option is B 26

The general electronic configuration of 3d series elements is $\left[Ar\right]3d^{1-10}4s^{1-2}$.
The given electronic configuration of the transition element 'X' in its +3 oxidation state is $\left[Ar\right]3d^5$. The element is present in its +3 oxidation state, which means that the element has lost 3 electrons.

Thus, the electronic configuration of the transition element 'X' in its ground state can be written as $\left[Ar\right]3d^{6}4s^2$.

Atomic number of an element is equal to the number of electrons present in ground state configuration of a neutral atom.

The electronic configuration $\left[Ar\right]3d^{6}4s^2$ means that the total number of electrons in 'X' is 26. Thus, the atomic number of transition element 'X' is 26.

Thus, option (B) is the correct answer.