What is the ground-state electron configuration of the $S^c$ ion?

• A. $A^r{4}^{s}2$
• B. $A^r{4}^{s}13^{d}1$
• C. $A^r{3}^{d}0$
• D. $A^r{3}^{d}1$

Answer: (C)

Verified step by step guidance

1. Identify the element and its atomic number: Scandium (Sc) has an atomic number of 21, meaning a neutral Sc atom has 21 electrons.
2. Write the ground-state electron configuration for neutral Scandium: Start from Argon (Ar) core configuration, which accounts for 18 electrons, then add the remaining electrons in the 4s and 3d orbitals. The configuration is \(\mathrm{[Ar]\ 4s^2\ 3d^1}\).
3. Determine the number of electrons removed for the Sc\(^{3+}\) ion: Since the ion has a +3 charge, it has lost 3 electrons compared to the neutral atom, so the ion has 21 - 3 = 18 electrons.
4. Remove electrons in the correct order: Electrons are removed first from the outermost shell, which is the 4s orbital, then from the 3d orbital. Remove 2 electrons from 4s and 1 electron from 3d to account for the +3 charge.
5. Write the electron configuration for Sc\(^{3+}\): After removing 3 electrons, the configuration corresponds to the Argon core only, which is \(\mathrm{[Ar]}\), meaning no electrons remain in the 4s or 3d orbitals.