When halogen elements react with group one metals they form halide salts.
Explanation:
The elements of group 17 are called halogens. These are six elements Fluorine, Chlorine, Bromine, Iodine, Astatine. Halogens are very reactive these elements can not be found free in nature. Their chemical properties are resemble greatly with each other. As we move down the group in periodic table size of halogens increases that's way fluorine is smaller in size as compared to other halogens elements. Their boiling points also increases down the group which changes their physical states. i.e fluorine is gas while iodine is solid.
When halogen elements react with group one metals they form halide salts.
Alkali metals have one valance electron and halogens needed one electron to complete the octet thus alkali metals loses one electron which is accepted by halogens atom and form ionic compound called halide salts.