[ General Glossary, Quantum Glossary, Atomic Glossary ]
Ground-State Configurations

Below are the Ground-State Configurations of the first few elements, followed by the astronomically abundant elements.
Atom Configuration Meaning
outer electrons have...
H (Z=1) 1s1 2S1/2 n=1 (ie K-shell)
only one outer electron, with l=0 (from the "s")
multiplicity=2 (ie spin S=1/2)
L=0 (from the "S")
J=1/2 (so 2J+1=2 states)
Even Parity (from lack of symbol)
He (Z=2) 1s2 1S0 n=1 (ie K-shell)
two outer electrons, with l=0 (from the "s")
multiplicity=1 (ie spin S=0)
L=0 (from the "S")
J=0 (so 2J+1=1 state)
Even Parity (from lack of symbol)
Li (Z=3) 1s2 2s1 2S1/2 n=2 (ie L-shell)
one outer electron, with l=0 (from the "s")
multiplicity=2 (ie spin S=1/2)
L=0 (from the "S")
J=1/2 (so 2J+1=2 states)
Even Parity (from lack of symbol)
Be (Z=4) 1s2 2s2 1S0 n=2 (ie L-shell)
two outer electrons, with l=0 (from the "s")
multiplicity=1 (ie spin S=0)
L=0 (from the "S")
J=0 (so 2J+1=1 state)
Even Parity (from lack of symbol)
B (Z=5) 1s2 2s2 2p1 2Po1/2 n=2 (ie L-shell)
one outer electron, with l=1 (from the "p")
multiplicity=2 (ie spin S=1/2)
L=1 (from the "P")
J=1/2 (so 2J+1=2 states)
Odd Parity
C (Z=6) 1s2 2s2 2p2 3P0 n=2 (ie L-shell)
two outer electrons, with l=1 (from the "p")
multiplicity=3 (ie spin S=1)
L=1 (from the "P")
J=0 (so 2J+1=1 state)
Even Parity (from lack of symbol)
N (Z=7) 1s2 2s2 2p3 4So3/2 n=2 (ie L-shell)
three outer electrons, with l=1 (from the "p")
multiplicity=4 (ie spin S=3/2)
L=0 (from the "S")
J=3/2 (so 2J+1=4 states)
Odd Parity
O (Z=8) 1s2 2s2 2p4 3P1 n=2 (ie L-shell)
four outer electrons, with l=1 (from the "p")
multiplicity=3 (ie spin S=1)
L=1 (from the "P")
J=1 (so 2J+1=3 states)
Even Parity (from lack of symbol)

Atom Configuration Meaning
outer electrons have...
Ne (Z=10) 1s2 2s2 2p6 1S0 n=2 (ie L-shell)
six outer electrons, with l=1 (from the "p")
multiplicity=1 (ie spin S=0)
L=0 (from the "S")
J=0 (so 2J+1=1 state)
Even Parity (from lack of symbol)
Mg (Z=12) 1s2 2s2 2p6 3s2 1S0 n=3 (ie M-shell)
two outer electrons, with l=0 (from the "s")
multiplicity=1 (ie spin S=0)
L=0 (from the "S")
J=0 (so 2J+1=1 state)
Even Parity (from lack of symbol)
Si (Z=14) 1s2 2s2 2p6 3s2 3p2 3P0 n=3 (ie M-shell)
two outer electrons, with l=1 (from the "p")
multiplicity=3 (ie spin S=1)
L=1 (from the "P")
J=0 (so 2J+1=1 state)
Even Parity (from lack of symbol)
S (Z=16) 1s2 2s2 2p6 3s2 3p4 3P2 n=3 (ie M-shell)
four outer electrons, with l=1 (from the "p")
multiplicity=3 (ie spin S=1)
L=1 (from the "P")
J=2 (so 2J+1=5 states)
Even Parity (from lack of symbol)
Fe (Z=26) 1s2 2s2 2p6 3s2 3p6 4s2 3d6 5D4 this is a bit tricky since the 4s subshell has a lower energy than the 3d subshell, thus the outer electrons are actually in the latter
n=3 (ie M-shell)
six outer electrons, with l=2 (from the "d")
multiplicity=5 (ie spin S=2)
L=2 (from the "D")
J=4 (so 2J+1=9 states)
Even Parity (from lack of symbol)