Isotonic compound have high melting point. Why ? Name the ions present in CaS. Pls answer fastly .. ​

a HBr is more ionic as Hydrogen having much smaller size and bromine having larger size whch may result in lower lattice energy in comparison to NaBr having size of sodium comparable to size of bromine and results in proper fixing of cation in lattice of anion contributes to higher lattice energy and required little bit higher energy to dissociate.

Thus, HBr is more ionic than NaBr.

b BrCl is more ionic as Chlorine having much smaller size and bromine having p pii- d pii interaction which contributes to larger size which may result in lower lattice energy in comparison to FCl having size of Florine  comparable to size of Chlorine and results in proper fixing of cation in lattice of anion contributes to higher lattice energy and required little bit higher energy to dissociate.

Thus, BrCl is more ionic than FCl