Putting the quantum numbers together

Table 1.1 summarizes the quantum numbers available for the first two energy levels.

Table 1.1 Quantum Numbers for the First Two Energy Levels

Table 1.1 shows that in energy level 1 (n = 1), there’s only an s orbital. There’s no p orbital because an l value of 1 (p orbital) is not allowed. And notice that there can be only two electrons in that 1s orbital (ms of +1⁄2 and –1⁄2). In fact, there can be only two electrons in any s orbital, whether it’s 1s or 5s.

Each time you move higher in a major energy level, you add another orbital type. So when you move from energy level 1 to energy level 2 (n = 2), there can be both s and p orbitals. If you write out the quantum numbers for energy level 3, you see s, p, and d orbitals.

Notice also that there are three subshells (ml ) for the 2p orbital and that each holds a maximum of two electrons. The three 2p subshells can hold a maximum of six electrons.

There’s an energy difference in the major energy levels (energy level 2 is higher in energy than energy level 1), but there’s also a difference in the energies of the different orbitals within an energy level. At energy level 2, both s and p orbitals are present. But the 2s is lower in energy than the 2p. The three subshells of the 2p orbital have the same energy. Likewise, the five subshells of the d orbitals have the same energy.