Principle quantum number

               The principal quantum number has the greatest effect on the electron shell or energy level of an atom. It has only positive integer value. It is denoted by 'n'. n can have values 1,2,3,4.. etc. The first level is also known as K level. Second as L level. Third as M level. Forth as N level and so on. The first K level is nearest to the nucleus and next one is second and so on. Principal quantum number is cited first in the set of four quantum numbers associated with an electron.It describe the size of the orbital. It measures the average distance of the electron from the nucleus, 'n' increases the orbital becomes larger and the electron farther from the nucleus.
For example; A hydrogen atom with n=1 the electron is in its ground state if the electron is in the n=2 orbitals , it is an excited state. The total number of orbitals for a given n value is n_2.