Why does the atomic radius of an element increase as you go down a group?

All of the scientists who contributed to the development of the periodic table arranged groups of similar elements in vertical columns. Commonly known groups are groups 1, 7 and 0. These have 'trivial names' - the alkali metals, the halogens and the noble gasses. The patterns in the periodic table are usually referred to as trends because the patterns are not exact and in some cases, you can't measure them directly e.g. reactivity of the alkali metals with water. Whilst there are some trends that run along the rows, the most important trends are found when you go down the groups. PLEASE... Show more

All of the scientists who contributed to the development of the periodic table arranged groups of similar elements in vertical columns. Commonly known groups are groups 1, 7 and 0. These have 'trivial names' - the alkali metals, the halogens and the noble gasses. The patterns in the periodic table are usually referred to as trends because the patterns are not exact and in some cases, you can't measure them directly e.g. reactivity of the alkali metals with water. Whilst there are some trends that run along the rows, the most important trends are found when you go down the groups.

PLEASE NOTE: There are different ways of numbering the groups of the periodic table. Uptill high school level chemistry, the number of electrons in the outer shell = number of group.At higher levels, you will find that this is no longer the case other than for groups 1 and 2. 

Show less