For which of the following element, all of its existing ion, M, will be diamagnetic? — Atomic Structure Chemistry Question

💡 Solution & Explanation

Sodium (Na) only forms the stable Na$^+$ ion by losing its single 3s valence electron. The resulting configuration is $[Ne]$, which has all electrons paired and is diamagnetic. Transition metals like Cu, Fe, and Cr form various ions that are paramagnetic (e.g., Cu$^{2+}$, Fe$^{2+}$, Cr$^{3+}$). Therefore, correct answer is D.