Section-D: Comprehension Type
A spinal is an important class of oxides consisting of two types of metal ions with the oxide ions arranged in ccp layers. The normal spinel has one–eighth of the tetrahedral holes occupied by one type of metal ion and one–half of the octahedral holes occupied by another type of metal ion. Such a spinel is formed by Mg2+, Al3+, Al3+ and O2–. The neutrality of the crystal is being maintained.
Type of hole occupied by Al3+ ions is :