The answer is: Cl2.
Chlorine is diatomic molecule made of two chlorine atoms.
Diatomic molecules are molecules made of two atoms.
They can be homonuclear (molecule made of two atoms of the same element) and heteronuclear (molecule made of two different atoms).
Chlorine (Cl) is halogen element.
Halogen elements are in group 17: fluorine (F), chlorine (Cl), bromine (Br) and iodine (I). They are very reactive and easily form many compounds.