In chemistry, you're likely to learn that each atom has a given number of orbitals, or electron shells, where the first orbital contains two electrons, the next contains eight electrons, and so on. In physics, you're likely to learn about electron excitation (electrons going from a lower energy level to a higher one) and photon emission (electrons returning from higher energy levels to lower energy levels). The concepts of orbitals and energy levels are clearly related - with each atom having a predetermined number of each - but the number of orbitals of an atom doesn't always (or ever, I'm not sure) equal the number of energy levels of that same atom.
For example; hydrogen has one orbital (containing one electron) but has 5 discrete energy levels at which the electron can exist.
If anyone could clear up my confusion it would be much appreciated. Thanks in advance!