A tube with bromine in it. At the bottom is bromine as a liquid and above it is bromine as a gas. The tube is sealed in an acrylic cube.

Bromine (Br) is a chemical element. Its atomic number (which is the number of protons in it) is 35, and its atomic weight is 80. It is part of the Group 7 elements (halogens) on the periodic table. It is diatomic, which means that two atoms are stuck together to make a molecule in any bromine sample.