F2,H2F_{2}, H_{2}F2,H2
CH4,Cl2\mathrm{CH}_{4}, \mathrm{Cl}_{2}CH4,Cl2
NH3,HCl\mathrm{NH}_{3}, \mathrm{HCl}NH3,HCl
N2,O2\mathrm{N}_{2}, \mathrm{O}_{2}N2,O2