The electron cloud model says that we cannot know exactly where an electron is at any given time, but the electrons are more likely to be in specific areas. These areas are specified by orbitals. The orbitals are specified by shells and sub-orbitals. In the Bohr model, electrons are assigned to different shells. The shells, k,l,m,n,o,p,q, each represent different levels of energy, and are also called energy levels. The sub-orbitals; s,p,d,f, are regions where it will be more likely to find electrons, and can each hold a different number of electrons. the s,p,d,f orbitals are all shaped differently. This can be proven by the repeating patterns of chemical properties in the periodic table. Using quantum mechanics, chemists can use the electron cloud model to assign electrons to different atomic orbitals. Atomic orbitals also explain the patterns in the periodic table. 