Why do groups I, II, & III easily form halide compounds?
& can you explain what a halide compound is?
A halide is a compound with a halogen. Halogens are the elements in group 17 (or group VIIA depending upon the system in use); namely, fluorine, chlorine, bromine, iodine.
Groups I, II, III are elements that have 1, 2, or 3 electrons in their outside shell and they want to lose those electrons. They are fairly easily removed, especially with the halogens.