On the periodic table, what is the group number of the halogens?

On the periodic table, the halogens occupy group 17.

Group 17 contains fluorine, chlorine, bromine, iodine, and astatine; tennessine is the superheavy member of the group. These elements have seven valence electrons in their neutral atoms, one short of a full outer shell.

Halogens commonly form negative ions with a one-unit charge, called halide ions. Chloride in salt and fluoride in some dental products are familiar examples. The name halogen comes from Greek roots meaning salt-former.

Older periodic-table systems may label this column VIIA or group VII, while the modern IUPAC numbering system calls it group 17. The neighboring group 18 contains noble gases, which generally have filled valence shells and much lower chemical reactivity.