Now, the principal quantum number gives the energy level of that electron. The second quantum number, known as the Zimmerfa quantum number gives or designates the shape of the orbital, and it's represented by the letter L, and it could be 00:12 and so on, zero being the S shape, one being the P shape, two being the D shape. The third quantum number specifies exactly which orbital that our electron is in. And the fourth quantum number gives the spin electron spin of our electron. So we could have either plus one half spin or minus one half spin. So in this lecture, we're only going to deal with the S or the P orbital.