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 charge, the more is 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(+1)(Al_(2)O_(3)) gt overset(+2)(CuO)`
Group ` implies 1" "2" "11`
Period `implies` 3rd rd 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)`