Provide the electron configuration of free Ni²⁺ ion and determine the number of unpaired electrons.

• A. [Ar]4s²3d⁸; 2 unpaired electrons
• B. [Ar]4s²3d⁶; 4 unpaired electrons
• C. [Ar]3d⁸; 2 unpaired electrons
• D. [Ar]3d⁶; 4 unpaired electrons

Answer: (C)