The periodic table is divided into two sections: d and f blocks. Transition metals are elements that belong to Groups 3 to 12. The d orbitals in these elements are entirely filled. The f block is made up of the two rows at the very bottom of the periodic table. This block is made up of elements with filled f orbitals. These are also referred to as inner transition elements. The f block is divided into two series: Lanthanide and Actinide.