[Mona lizza]

As we know that when n=5 azimuthal quantum numbers has value 0,1,2,3,4 it means that 5 shell consist s,p,d,f,g orbital,but we know that g never appear in any atom so n-1 rule is wrong?

[mjc123]

No known atom has electrons in a g orbital in the ground state, but that doesn't mean that g orbitals don't exist. Electrons can occupy g orbitals in an excited state.
Currently recognised elements go up to 118 (oganesson), with complete 7s, 5f, 6d and 7p shells. Once you get beyond that (if you do), you will start filling up 8s, then perhaps 5g, etc.

[Mona lizza]

I have red somewhere that when n=5 azimuthal quantum number 0,1,2,3,4(we skip 3) why + if there is g orbital also than what is its shape

[mjc123]

Google "g orbital shapes"

[Enthalpy]

http://winter.group.shef.ac.uk/orbitron/