According to Neils Bohr, the atomic structure is described as electrons orbiting around the nucleus in orbitals. Each orbital holds two electrons that are oppositely spinning, according to Pauli's Exclusion Principle. These orbitals are then located in sub-shells of varying energy levels. There are 4 types of these sub-shells. In order of decreasing energy, they are the s, p ,d and f sub-shells. They differ in shape and energy levels. The s sub-shell holds 1 orbital, p holds 3, d holds 5 and f holds 7 orbitals. These sub-shells are oriented according to their principal quantum number, n. There are a total of 7 energy levels with 1 being the strongest and closest to the nucleus, and 14 being the weakest and farthest to the nucleus. You will see that electrons are filled from the strongest 1s orbitals, to the weakest 7f orbital.
Thus, in the energy level n=3, there are 3s, 3p, 3d and 3f sub-shells. The total electrons for this energy level is. therefore,
Noble gasses are extremely unreactive. They are called 'noble' because they do not mix with almost any other element, save flouride. They all, except helium, have a complete first and second valence level, meaning ten total electrons. Because of this they are very stable and do not want to receive any electrons or give any.
0 degrees and 101 kPa are the conditions that describe the standard temperature and pressure. When expressed in K, the standard temperature 0 degrees equals 273.5 K. Also the standard pressure 101 kPa equals 760 mmHg or 1 Atm.