Nuclear & Particle Physics - Spectroscopic Notation

Sodium has eleven electrons and the sequence in which energy levels fill in atom is 1s, 2s, 2p, 3s, 3p, 4s, 3d, etc. What is the ground state of sodium in the usual notation 2s+1Lj?
A. 1S0
B. 2S1/2
C. 1P0
D. 2P1/2
E. 3P1/2
(GR8677 #84)
Solution:

11 electrons → 1s2, 2s2, 2p6, 3s1

3s1 → 1 electron with spin ½ → s = 1/2 → multiplicity = 2s + 1 = 2(1/2) + 1 = 2

3s1 → Subshell sl = 0 → j = l + s = 0 + 1/2 = 1/2

3s1 → Subshell sL = S

Spectroscopic Notation: 2s+1Lj2S1/2

Answer: B

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