Understanding the Face-Centered Cubic (FCC) Structure
* Unit Cell: The FCC structure is characterized by atoms at each corner of a cube and in the center of each face.
* Coordination Number: In an FCC structure, each atom has a coordination number of 12, meaning it's directly surrounded by 12 other atoms.
Applying it to MgO
1. Ionic Arrangement: In MgO, Mg²⁺ ions occupy the positions that Na⁺ ions would occupy in NaCl, and O²⁻ ions occupy the positions that Cl⁻ ions would occupy.
2. Coordination Number: Since the structure is FCC, each Mg²⁺ ion is surrounded by 12 nearest neighbors, which are all O²⁻ ions.
Therefore, there are 12 oxide ions (O²⁻) surrounding each magnesium ion (Mg²⁺) in the MgO crystal structure.
