Arrange the following ions in increasing
`Na^+, Mg^(2+), Al^(3+)`
(i) extent of hydration
(ii) size of the hydrated ions
(iii) ionic mobility

Explanation

`{:(,"Ion", Be^(2+), Cl^(-),S^(2-),Na^(+),Mg^(2+),Br^(-)),(,"Valence shell",1,3,3,2,2,2):}`
Now, between `Na^(+) and Mg^(2+), ""(12)_Mg^(2+) lt ""11_Na^(+)` (Isoelectronic) also, between `Cl^(-) and S^(2-), ""(17)_Cl^(-) lt ""(16)S^(2-)` (isoelec tronic) because for iso-electronic species size decreases as the atomic number increases. Hence the order of increasing size is : `Be^(2+) lt Mg^(2+) lt Na^(2+) lt Cl lt S^(2-) lt Br^(-)`