What are the group in chemistry

In chemistry, a group refers to a vertical column in the periodic table. Elements within the same group share similar chemical properties because they have the same number of valence electrons (electrons in the outermost shell).

For example, Group 1 elements (like Lithium, Sodium, Potassium) are alkali metals and are highly reactive. Group 17 elements (like Fluorine, Chlorine, Bromine) are halogens and are also very reactive nonmetals.