👉 Halides are a class of compounds that contain one or more electrons in their outermost shell, typically in the 1s or 2s orbital. They have a chemical reactivity that varies depending on the number and type of electrons in their outermost shells. For example, some halide salts (like sodium chloride) contain three or four hydrogen atoms, while others like potassium chlorate contain only two hydrogen atoms due to the presence of a lone pair of electrons in the outermost shell.