Answers

2015-02-25T18:18:36+05:30
Al is aluminium O2 is oxygen Al has a valency of 3& o2 of 2 We know that valencies are exchanged while forming compounds So it forms Al2O3
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2015-02-27T04:52:02+05:30
We derive a chemical formula of a compound by cross cross method. In this the valency of the two are interchanged. So the valency of O is interchanged with the valency of Al .
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