Main-group element

Main group elements are the groups of elements in the periodic table. These groups are numbered 1-18 down the left side of the table. Each element in a group has the same number of electrons in its outermost energy level. For example, all of the elements in group 1 (the far left column) have 1 electron in their outermost energy level. The elements in group 2 have 2 electrons in their outermost energy level. The elements in group 3 have 3 electrons in their outermost energy level, and so on. All of the elements in each group are really similar to each other because they all have the same number of electrons in their outermost energy level.