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(I) Lithium forms monoxide with oxygen whereas sodium forms peroxide with oxygen. Why? (II) Write about the uses of strontium? |
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Answer» (I) 1. The fact that a small cation can stabilize a small anion and a large cation can stabilize a large anion explains the formation and stability of the oxides. 2. The size of Li+ ion is very small and it has a strong positive field around it. It can combine . with only small anion, O2- ion, resulting in the formation of monoxide Li2O. 3. The Na+ ion is a larger cation and has a weak positive field around it and can stabilize a bigger peroxide ion, \(O^{2-}_2\) or [-O-O-]2- resulting in the formation of peroxide Na2O2. (II) 1. 90Sr is used in cancer therapy. 2. 87Sr/86Sr ratio is used in marine investigators as well as in teeth, tracking animal migrations or in criminal forensics. 3. Dating of rocks. 4. Strontium is used as a radioactive tracer in determining the ‘source of archaeological materials ’ such as timbers and coins. |
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