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...