How many electrons are there in #Br^-#?

1 Answer
Nov 16, 2015

The #"Br"^(-)"# ion has 36 electrons.


The atomic number for bromine is 35, which means it has 35 protons in its atomic nuclei. A neutral bromine atom would also have 35 electrons. In order for a bromine atom to become a #1-# bromide ion, it would have to gain an additional electron.

Below is the Lewis dot structure for a neutral bromine atom, which has seven valence electrons.
Below is the Lewis dot structure for a #"Br"^(-)"# ion, which has eight valence electrons. The extra valence electron gives it a negative charge.

The diagram below shows how a bromine atom gains an electron from the element lithium in order to form the ionic compound LiBr.