# 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 $\left(\text{_57"La}\right)$ and hafnium $\left(\text{_72"Hf}\right)$ in period 6 and between actinium $\left(\text{_89"Ac}\right)$ and rutherfordium $\left(\text{_104"Rf}\right)$ in period 7.