How many electron levels exist?

1 Answer
May 15, 2018

As many as the atom needs.


In reality, electron energy levels are "accessed" as soon as the electron "occupies" an orbital in a new energy level. Energy levels of empty orbitals don't really exist. We just like to say they do for simplicity, and draw, e.g.

ul(uarr darr)

for a 1s energy level "occupied" by two electrons.

The usual orbitals atoms have often used (grouped by angular momenta) are:

1s, 2s, 3s, 4s, 5s, 6s, 7s
2p, 3p, 4p, 5p, 6p, 7p
3d, 4d, 5d, 6d
4f, 5f

No atom has so far used a 5g orbital yet, so they do not exist yet. They're not there until they're needed. If we ever get to element number 121, we might have a chance of seeing a 5g orbital being used, but since those are so radially compact and have 4 angular nodes, we might need to wait even longer than that...