What are all the halogens?

These are literally the $\text{salt-forming}$ elements of $\text{Group 17}$ in the Periodic Table.
And the individual members are: fluorine; chlorine; bromine; iodine....As the element they are binuclear, i.e. ${X}_{2}$, and they are potent oxidants, readily forming halide ions, ${X}^{-}$. Fluorine, ${F}_{2}$, in particular is the most reactive element on the Periodic Table.