Ncert Exercises & Solutions

Which pair of ions has the same electronic configuration?

1.	\(Cr^{3+}, Fe^{3+}\)	2.	\(Fe^{3+}, Mn^{2+}\)
3.	\(Fe^{3+}, Co^{3+}\)	4.	\(Sc^{3+}, Cr^{3+}\)

Hint: Draw the electronic configuration of each ion and check the same configuration

The electronic configuration of ions is as follows:

{}_{24}{Cr} = [Ar] 3 d^{5}, 4 s^{1}

{}_{26}{Fe} = [Ar] 3 d^{6}, 4 s^{2}

{}_{25}{Mn} = [Ar] 3 d^{5}, 4 s^{2}

{}_{27}{Co} = [Ar] 3 d^{7}, 4 s^{2}

{}_{21}{Sc} = [Ar] 3 d^{1}, 4 s^{2}

{}_{24}{Cr}_{3 +} = [Ar] 3 d^{3}

{}_{26}{Fe}_{3 +} = [Ar] 3 d^{5}

{}_{25}{Mn}_{2 +} = [Ar] 3 d^{5}

{}_{27}{Co}_{3 +} = [Ar] 3 d^{6}

{}_{21}{Sc}_{3 +} = [Ar]

Thus, Fe³⁺ and Mn²⁺ have the same electronic configuration.