text: Actually,  N has to do with the amount of electrons that the element has. the first level has a maximum of two electroins, so all elements that have under 2 electrons will be in this level (hydrogen has 1 e, He has 2). The 2nd energy level can hold up to 8 electrons, so look at the atomic number (# of electrons and determine which energy level it would be under). N=3, maximum number of electrons is from 9-18)