Which of the following oxides is most basic ?

Options

A. `Na_(2)O`
B. `MgO`
C. `Al_(2)O_(3)`
D. `CuO`

Answer

A

Explanation

Applying Fajans' rule, the lower, the more in ionic and the more is basic and vice versa.
Moreover, small cation, large anion, high charge and presence of d electrons mean more covalent and more acidic.
Therefore, decreasing order of basic nature is
`{:(,overset(+1)(Na_(2)O) gt,overset(+2)(MgO) gt,overset(+3)(Al_(2)O_(3)) gt,overset(+2)(CuO)),("Group" .rArr,1,2,13,11),("Period" .rArr,3rd,3rd,3rd,4th):}`
Size `Al^(3+) gt Cu^(2+)` and presence of d electron in `Cu^(2+)` makes it less basic (or more acidic) than `Al_(2)O_(3)`.