Difference between a halogen and a halide? Explain using chemical formulas.
A halogen is an element, as in F2, Cl2, Br2, I2.
A halide is a salt of the halogen; i.e., a compound of a metal + halide.
For example, Cl2, a halogen, combines with Na(a metal) to form NaCl (a halide--more specifically it is a sodium halide. In like manner you could have KCl, CsCl, etc.