In chemistry and atomic physics, the main group is the group of elements whose lightest members are represented by helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, and fluorine as arranged in the periodic table of the elements
the representative elements are elements where the the s and p orbitals are filling. The transition elements are elements where the d orbitals (groups 3-11 on the periodic table) are filling, and the inner transition metals are the elements where the f orbitals are filling.
