Arrange the following ions in the order of increasing size.

Be²⁺, Cl- ,S^2- ,Na⁺, Mg²⁺,Br^-

Also please explain why?

Cations lose electrons and are smaller than the parent ion. While anions add electrons and are larger than the parent ion. We also know that ionic size decreases with an increasing nuclear charge.

The given list of ions are: Be2+, Cl- ,S2- ,Na+, Mg2+,Br-

We know that size of cations increases down the group and decreases across the period,

In the given list Be2+ is the only cation with highest nuclear charge hence least in size followed by Mg2+ and then Na+.

Among S2- and Cl- (isoelectronic) as nuclear charge increases in an isoelectronic series the ions become smaller) Cl- is smaller than S2-.

As we know size of anions increases down the group and decreases across the period, S2- is bigger in size than Cl- and Br- is bigger in size than both S2- and Cl-. Finally least in size would be Be2+ and largest in size is Br-.

Therefore the increasing order of sizes of ions is:

Be2+<Mg2+<Na+<Cl-<S2-<Br-