How Many Protons for a 5g Orbital Electron Configuration?

[Razael]

Homework Statement

Using a strict interpretation of the n+l rule, how many protons would an atom need to create a ground state electron configuration with one electron in a 5g orbital? Give electron configuration.

Homework Equations

The Attempt at a Solution

g is an l value of 4, 4+5 = 9. So 5g is filled after other orbitals with n+l's lower than 9, or equal but with higher n values.

This puts 5g after 9s, does it not? I have no clue what to do from here.

 

[Borek]

Atom is neutral - that means charge of electrons and charge of nucleus cancel out, they are identical (just one is positive, other negative).

 

[Razael]

The answer (which is given) is 121 protons. Since the atom is neutral, there'd also be 121 electron, so I'd look for an electron configuration where all orbitals before 5g + 1 = 121.

I don't know what 5g comes after though.

 

[Borek]

n+l lower then 9 means 8 max, that in turn means 8+0:

http://en.wikipedia.org/wiki/File:Electron_orbitals.svg

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methods

 

[Razael]

Okay, added up all electrons up to and including 8s and got 120. Adding one for 5g gives me 121.

I still don't understand why it has to be preceded by 8s though. Why not, say, 6d?

 

[Borek]

http://en.wikipedia.org/wiki/Aufbau_principle