So these four quantum numbers is like the ID badge of that unique electron. So let's look at these four quantum numbers. The first quantum number is called the principal quantum number, N. So it's represented by the lowercase letter N. And this number begins with one and could be 2345. So N has to be a positive whole number. Now, this quantum number, the principal quantum number, designates the shell level or the energy level in which the electron is located. The Larger the n, the Larger Our size or The Larger The Size Of The Atom and The Greater The energy.