Electronic confriguration of a transition element X in +3 oxidation states is `[Ar]3d^(5)`.
What is its atomic number?

Explanation

Electronic configuration of `X^(3+) = [Ar] 3d ^(5)`
During oxidation of X to `X^(3+) ` two elements of 4s shell are removed first and then the removal of 3d- elecrtron occurs. Since in all three electrons are lost therefore two of these are 4s- orbital electrons and more is 3d- orbital electron.
Here [Ar] stands for argon whose atomic number = 18 .
`:. ` Electronic configuration of `X= [Ar] 3d^(6) 4s^(2)`
Thus the atomic number of the transition element = 18 + 6 + 2 = 26 `