Which of the following ion have the same number of unpaired electrons as in Fe ()? — Atomic Structure Chemistry Question

💡 Solution & Explanation

Fe$^{2+}$ ($Z=26$) is $[Ar] 3d^6$, having 4 unpaired electrons. (a) Fe$^{3+}$ is $3d^5$ (5 unpaired). (b) Ni$^{2+}$ is $3d^8$ (2 unpaired). (c) Co$^{3+}$ is $3d^6$ (4 unpaired). (d) Cr$^+$ is $3d^5$ (5 unpaired). Co$^{3+}$ matches Fe$^{2+}$. Therefore, correct answer is C.