Which of the following ions has electronic configuration $[\mathrm{Ar}] 3 d^{6}$ ?\ (At. nos. $\mat

Question

Which of the following ions has electronic configuration $[\mathrm{Ar}] 3 d^{6}$ ?\ (At. nos. $\mathrm{Mn}=25, \mathrm{Fe}=26, \mathrm{Co}=27, \mathrm{Ni}=28$ )\

Professor PC Thomas Classes · Answer

(d) : The electronic configuration of the given ions is\ $\mathrm{Ni}^{3+}:[\mathrm{Ar}] 3 d^{7} 4 s^{0}, \quad \mathrm{Mn}^{3+}:[\mathrm{Ar}] 3 d^{4} 4 s^{0}$\ $\mathrm{Fe}^{3+}:[\mathrm{Ar}] 3 d^{5} 4 s^{0}, \quad \mathrm{Co}^{3+}:[\mathrm{Ar}] 3 d^{6} 4 s^{0}$\ Thus, $\mathrm{Co}^{3+}$ is the ion with the desired configuration.