A chemical family consists of elements on the periodic table that belong to a group. Elements in a chemical family share similar chemical characteristics or physical properties. For example, depending on their location from left to right on the periodic table, elements in each chemical family also exhibit certain trends in things, such as atomic radii or sizes.
On the periodic table, one can find a group or family by looking down the vertical columns. The group numbers from left to right at the top of the periodic table, which range from 1 through 18, denote the different groups or chemical families. For example, the noble gases are in Group 18. This is a chemical family of elements that share many properties, such as these elements have eight valence electrons and are non-reactive. Some noble gases are argon, helium and neon.
Similarly, there are other different chemical families. The elements in Group 1 are the alkali metals. These elements include sodium and potassium, which also have one valence electron. While Group 2 are the alkaline earth metals like magnesium and calcium, the elements in Group 17 are the halogen gases and include chlorine and fluorine.
Some other examples of chemical families are the transition metal groups and the nitrogen group. The transition elements are the 38 elements belonging to Groups 3 through 12 of the periodic table. The nitrogen group is Group 15.