Which of the following orders of ionic radii is correctly represented?

Options

A. `H^(-) gt H^(+) gt H`
B. `Na^(+) gt F^(-) gt O^(2-)`
C. `F^(-) gt O^(2-) gt Na^(+)`
D. `Al^(3+) gt Mg^(2+) gt N^(3-)`

Answer

A

Explanation

(a) `H^(-) gt H^(+) gt H`
It is known that radius of a cation is always smaller than that of a neutral atom due to decreas in the number of orbits. Whereas, the radius of anion is always greater than a cation due to desrease in effective nuclear charge. Hence, the correct order is
`H^(-) gt H gt H^(+)`
`Na^(+) gt F^(-) gt O^(2-)`
The given species are isoelectronic as they contain same number of electrons. For isoelectronic species,
`"Iodic radii" prop (1)/("atomic number")`
`{:(,"Ion:", Na^(+),F^(-),O^(2-)),(,"Atomic number:", 11,9,8):}`
Hence, the correct order of ions radii is
`O^(2-) gt F^(-) gt Na^(+)`
(c) Similary, the correct options is
`O^(2) gt F^(-) gt Na^(+)`
(d) `{:("Ions":,Al^(3+)Mg^(2+)N^(3-)),("Atomic number":, 13" "12" "7):}`
Hence the correct order is `N^(3) gtMg^(2+) gt Al^(3+)`