QUANTUM NUMBERS

The quantum mechanic model describes the energy levels of the electrons in three dimensional spaces (orbitals).
There are a set of 4 quantum numbers.

1. Principle Quantum Number (n)
2. Azimuthal Quantum Number (l) or Angular Momentum Quantum Number
3. Magnetic Quantum Number (m)
4. Spin Quantum Number (s)

These quantum numbers describe the energy level of an orbital and define the shape and orientation of the region in space where the electron is most likely to be found.

You can read more about quantum numbers by referring to this website: http://chemwiki.ucdavis.edu/Physical_Chemistry/Quantum_Mechanics/10%3A_Multi-electron_Atoms/Quantum_Numbers