Some help with chemical equations please :)?

Hcbiochem is correct - fluorine, chlorine, and bromine when by themselves all have a subscript of 2 so they would be written as F2, Cl2, and Br2. All halogens by themselves in chemical equations are written with a subscript of 2. Oxygen, nitrogen, and hydrogen by themselves also have a subscript of 2. A good way to remember the diatomic molecules as they are called is to remember this phrase: "Having dinner with my Uncle HONCLBrIF" H2 O2 N2 Cl2 Br2 I2 F2