Question

Consider the following species:
`N^(3-)`,`O^(2-)`,`F^(ө)`,`Na^(o+)`,`Mg^(2+)` and `Al^(3+)`
a. What is common in them?
b. Arrange them in the order of increasing ionic radii.

Answer 1

(a) Each of the given species (ions) has the same number of electrons (10 electrons). Hence, the given species are isoelectronic.
(b) The ionic radii of isoelectronic species increases with a decrease in the magnitudes of nuclear charge.
The arrangement of the given species in order of their increasing nuclear charge is as follows:
`N^(3-) lt O^(2-) lt F^(-) lt Na^(+) lt Mg^(2+) lt Al^(3+)`
Nuclear charge = +7 +8 +9 +11 +12 +13
Therefore, the arrangement of the given species in order of their increasing ionic radii is as follows:
`Al^(3+) lt Mg^(2+) lt Na^(+) lt F^(-) lt O^(2-) lt N^(3-)`