Answer: C. It is a negative ion that has one more valence electron than a neutral bromine atom.
A bromine element is a halogen. This means it has seven electrons in its valence shell. This makes Bromine very reactive as a result of the constant need to accept one electron into its outermost shell to achieve a balanced state. When a bromine element accepts one electron, it changes into a Bromine ion and then possesses a balance octet shell. A Bromide ion, therefore, is a negative ion with one more valence electron than a neutral Bromine atom.