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EastWind [94]
4 years ago
10

The Al2O3 crystal structure (corundum) consists of an HCP arrangement of O2- ions; the Al3+ ions occupy octahedral positions. Wh

at fraction of the available octahedral positions are filled with Al3+ ions? In corundum, the Al3+ ions do not fill the tetrahedral positions.
Chemistry
1 answer:
vesna_86 [32]4 years ago
5 0

Answer:

The fraction of the available octahedral positions are filled with Al^{3+} ions is \frac{2}{3}

Explanation:

If there are n numbers of spheres in HCP in packing:

Number of octahedral void = n

Number of tetrahedral void = 2n

Total number of voids = n + 2n = 3n

The Al_2O_3 crystal structure consists of an HCP arrangement of O^{2-}ions.

Number of spheres in HCP = 6

Number of O^{2-} = 6

Number of octahedral voids = 6

Number of tetrahedral void = 12

Number of aluminum ions when there are 6 O^{2-} ion =\frac{2}{3}\times 6= 4

Number of voids in which Al^3+ ions are present = 4

The fraction of the available octahedral positions are filled with Al^{3+} ions = \frac{4}{6}=\frac{2}{3}

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