Trends in the variation of properties

The physical properties of elements depend in part on their valence electron configurations. As this configuration remains the same within a group, physical properties tend to remain somewhat consistent. The most notable within-group changes in physical properties occur in Groups 13, 14, and 15, where the elements at the top are non-metallic, while the elements at the bottom are metals.

The group 17 of the modern periodic table consists of fluorine, chlorine, bromine, iodine and astatine. These elements are known as halogens. Halogen is a Greek word which means salt producer. These elements are called salt producers because chlorine, bromine and iodine are highly electronegative in nature and form anions that constitute the anionic part of salts found in the sea water. The last element of the group, astatine is radioactive in nature. All these elements belong to the p block of the modern periodic table. After the alkali group, halogen family constitutes the most homogenous group in the modern periodic table.

A group is a vertical column in the periodic table of the chemical elements. There are 18 groups in the standard periodic table, including the d-block elements but excluding the f-block elements. Each element within a group has similar physical or chemical properties because of its atom's outermost electron shell .