Question

The radii of the lithium and magnesium ions are 76 pm and 72 pm, respectively. Which compound has stronger ionic attractions, fithium oxide or magnesium oxide?

Answer 1

Magnesium oxide has stronger ionic attraction

Step-by-step explanation:

Ionic attraction force (F) is represented as-

`F=k(\mid q_(+)q_(-)\mid )/((r_(+)+r_(-))^(2))`

where k is constant,
`q_(+)` is charge on cation,
`q_(-)` is charge on anion,
`r_(+)` is radius of cation and
`r_(-)` is radius of anion.

Here anion for both oxides is
`O^(2-)`. So, for both of them
`r_(-)` is same.

For lithium oxide
`(Li_(2)O)`, cation is
`Li^(+)`. So,
`q_(+)` is +1.

For magnesium oxide (MgO), cation is
`Mg^(2+)`. So
`q_(+)` is +2

Hence
`\mid q_(+)q_(-)\mid (Li_(2)O)< \mid q_(+)q_(-)\mid (MgO)`.

As, radius of lithium ion is greater than radius of magnesium ion therefore-

`(r_(+)+r_(-))(Li_(2)O)> (r_(+)+r_(-))(MgO)`

So altogether
`F(MgO)> F(Li_(2)O)`