Energy levels of three or above can contain five d-orbitals. Each orbital can contain a pair of electrons. Each d-orbital can hold two electrons, resulting in a possible total of ten electrons in the d-orbitals of each of those energy levels.
D-orbitals are shaped like dumbells. They sit at a right angle along a three-dimensional axis. The size of the orbital increases as the energy level increases. In addition to the five d-orbitals, energy levels can contain one s-orbital. Energy levels of two or above can contain three p-orbitals, while energy levels of four and above can contain seven f-orbitals.