electronic configuration of x+2 and y+3 are: x+2= [Ar] 3d8 , y+3= [Ar]3d3. what are the atomic number of x0 and y0 resp.

A)28,24 B) 28,25 C)28,26 D)28,87

ans..C) 28,26...........how??

An ion shows an oxidation state of +2 when it loses two electrons. We are given that the electronic configuration of X²⁺ ion is [Ar]3d⁸. This means that the X contains two electrons more than X²⁺ ion, and so its electronic configuration will be [Ar]3d⁸4s². Thus, the number of electrons in X (or the atomic number of X) will be 

= 18 (Ar denotes argon, which has 18 electrons) + 2 + 8

= 28

Similarly, let us consider Y³⁺ ions. It will be formed when a Y atom loses three electrons. We are given that the electronic configuration of Y³⁺ ion is [Ar]3d³. This means that the Y contains three electrons more than Y³⁺ ion, and so its electronic configuration will be [Ar]3d⁵4s¹. Thus, the number of electrons in Y will be 

= 18 (Ar denotes argon, which has 18 electrons) + 1 + 5

= 24

So, the correct answer is (a) 28, 24 and not (c) 28, 26.