Which block of the periodic table is the largest?
The f-block consists of two periods of 14 elements. There are 14 elements because the f-sublevels are being filled and an f-sublevel can contain a maximum of 14 electrons in its 7 orbitals. These elements are in periods 6 and 7 between lanthanium
The f-block is usually written below the main body of the periodic table because of its length, but some periodic tables, called extended or expanded periodic tables will place them within the body of the periodic table.
Extended Periodic Table