Question

in which of the following groups of ions are the charges all shown correctly?

li-, o²-, s²+

ca²+, al³+, br-

k²-, f-, mg²+

na+, i-, rb-

Explanation:

• For \(Li\), it loses 1 electron to form \(Li^{+}\), not \(Li^{-}\). For \(S\), it gains 2 electrons to form \(S^{2 -}\), not \(S^{2+}\). So the group \(Li^{-},O^{2 -},S^{2+}\) is incorrect.
• \(Ca\) loses 2 electrons to form \(Ca^{2+}\), \(Al\) loses 3 electrons to form \(Al^{3+}\), and \(Br\) gains 1 electron to form \(Br^{-}\). This group \(Ca^{2+},Al^{3+},Br^{-}\) has correct charges.
• \(K\) loses 1 electron to form \(K^{+}\), not \(K^{2 -}\). So the group \(K^{2 -},F^{-},Mg^{2+}\) is incorrect.
• \(Rb\) loses 1 electron to form \(Rb^{+}\), not \(Rb^{-}\). So the group \(Na^{+},I^{-},Rb^{-}\) is incorrect.

Answer:

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