1st  Principle QN n 
2nd  Orbital QN l 
3rd  Magnetic QN m_{l} 
4th  Spin QN m_{s} 
n = 1,2,3...7 
l goes from 0 to n1 within an energy level l values = 0 (for s) , 1(for p) , 2 (for d), 3 (for f) sublevels 
Values of m_{l} go from +l to  l , which gives 2l + 1 number of values 
has 2 values: 
1. measures the average distance of the e^{} from the nucleus 
1. indicates the shape of the orbital ( set of probable locations of the e^{ }) 
1. identifies the direction in e^{} orbital has around the nucleus 
1. identifies the "spin" or rotation of the e^{} about its own axis 
2. different values of n mean different energy levels 
2. diff. values of l mean diff sublevels. In a sublevel all the e^{} have nearly the same energy. 
2. specifies the e^{} orbital in which the e^{} is located within a sublevel. 
2. shows that each orbital can contain only 2 e^{} 
3. different values of n mean relatively large differences in the energies of the e^{}s 
3. different sublevels within the same level may have moderately large differences in energy. 
3. different values of m_{l} mean little difference in energies of the e^{} 
3. the direction of spin is either in one direction or the other 
4. the smallest avgerage distance and the lowest energy occurs when n = 1; each increase in n increases those quantities. 
4. within any level, the lowest energy sublevel is s, then p, then d, then f. 
4. the number of possible values of m_{l} within a sublevel idenities how many e^{} pairs that the sublevel can hold 
4. when 2 e^{} (in an atom) have the same set of QN except for m_{s} , then these e^{} are called an e^{} pair 
5. the number of e^{} possible in a level is 2n^{2} 
5. the number of possible values of l for a level is equal to the value of n 

5.these e^{} within an e^{} pair have essentially the same energy 
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