http://www.dce.k12.wi.us/srhigh/teachers/bheeren/diatomic_elements1.htm
Seven Diatomic Elements
H2, O2, N2, F2, Br2, I2, Cl2
You should know that the following elements exist as diatomic
molecules. One acronym that is used is like a person’s name… HON F
BrICl (With HON being the first name, F being the middle initial,
and BrICl being the last name)
Hydrogen H2
Oxygen O2
Nitrogen N2
Fluorine F2
Chlorine Cl2
Bromine Br2
Iodine I2
Note: The fact that these elements are diatomic only relates to
these elements as isolated, neutral atoms. For instance, chlorine
when in a compound can be NaCl or CaCl2 or AlCl3. The number of
chlorine atoms depends on the charge of the atom with which the
chlorine is paired.