Question

in which of the following groups of ions are the charges all shown correctly?
○ k²-, f-, mg²+
○ li-, o²-, s²+
○ na+, i-, rb-
○ ca²+, al³+, br-

Explanation:

• For the first option: \(K\) (potassium) typically forms \(K^{+}\) ion, not \(K^{2 -}\). So this option is incorrect.
• For the second option: \(Li\) (lithium) forms \(Li^{+}\) ion (not \(Li^{-}\)), and \(S\) (sulfur) forms \(S^{2 -}\) ion (not \(S^{2+}\)). So this option is incorrect.
• For the third option: \(Rb\) (rubidium) forms \(Rb^{+}\) ion (not \(Rb^{-}\)). So this option is incorrect.
• For the fourth option: \(Ca\) (calcium) forms \(Ca^{2+}\) ion, \(Al\) (aluminum) forms \(Al^{3+}\) ion, and \(Br\) (bromine) forms \(Br^{-}\) ion. All charges are correct.

Answer:

\(Ca^{2+},Al^{3+},Br^{-}\) (the fourth option)