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In sapphire, oxide ions are arranged in ...

In sapphire, oxide ions are arranged in hexagonal close packing and aluminium ions occupy two-thirds of the octahedral voids. What is the formula of sapphire?

Text Solution

Verified by Experts

Let the number of oxids ions = 60
Number of `Al^(3+)` ions `=2//3xx"No. of octahedral voids"`
`=2//3xx60=40`
The ratio of `Al^(3+)` ions to `O^(2-)` ions `=40:60=2:3`
`therefore" Formula of the compound" = Al_(2)O_(3)`
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