Normal Spinel: The divalent A +2 ions occupy the tetrahedral voids, whereas the trivalent B +3 ions occupy the octahedral voids in the close packed arrangement of oxide ions. A normal spinel can be represented as: ( A +2 ) tet ( B +3 ) 2 oct O 4

The mineral spinel MgAl 2 O 4 has a normal spinel structure. In a normal spinel structure, the ions are in the following positions, where i, j, and k are arbitrary integers and δ, ε, and ζ are small real numbers (note that the unit cell can be chosen differently, giving different coordinates): [16]

Examples of normal and inverse spinel structures: MgAl 2 O 4 is a normal spinel since both Mg 2 + and Al 3 + are non-transition metal ions and thus CFSE = 0. The more highly charged Al 3 + ion prefers the octahedral site, where it is surrounded by six negatively charged oxygen atoms.

For a normal spinel, the total CFSE wold be: $$\Delta_{T}(A)+2\Delta_{O}(B)=\Delta_{T}(A)+\Delta_{O}(B)+\Delta_{O}(B)$$ and for an inverse spinel $$\Delta_{O}(A)+\Delta_{T}(B)+\Delta_{O}(B)$$ with $\Delta_{T}$ being the tetrahedral and $\Delta_{O}$ being the octahedral splitting energy of $\ce{A^2+}$ and $\ce{B^3+}$, respectively.