One molecule of chlorine gas has the formula \\[Cl_{2}\\]. Chlorine has only one chemical symbol: Cl. \\[H_{2}\\], \\[N_{2}\\], \\[O_{2}\\], and \\[Cl_{2}\\] are diatomic molecules that exist in gases such as hydrogen, nitrogen, oxygen, and chlorine. One molecule of gas, such as Cl–-Cl, has two atoms bonded by a covalent bond.