Question

What the symbol for an element that is a halogen?

Answer 1

We usually use the `X` symbol for substitution of halogen atoms.

Explanation:

For halogenation of olefins, we would thus write,

`H_2C=CH_2 + X_2 rarr XCH_2-CH_2X`

In general `X=Cl, Br`. Iodine tends to be a little bit expensive. Fluorine chemistry is the preserve of specialists, because `F_2` is extremely and dangerously reactive.