Halogens are compound of Group 17 of the periodic table. It's properties are:
Down the group the melting and boiling point of the elements increases, so, Fluorine will have the lowest whereas, Astatine will have the highest.
Down the group reactivity of halogens decreases, Fluorine reacts instantly whereas, iodine need to be heated strongly for reaction to take place.
Alkali metals are compound of Group 1 of the periodic table. It's properties include:
Alkali metal have low melting point and down the group melting point decreases i.e. Lithium have the melting point of 180 degree Celsius whereas, Cesium have the melting point of 28 degree Celsius only.
Down the group reactivity of these metal increases For example, Cesium reacts with Chlorine more vigorously as compare to reaction of Potassium with Chlorine.
