Symmetry - Methods of Molecular Quantum Mechanics - page 265

belong, using lower case letters preceded by a principal quantum number
n specifying the order of the orbital energies (Roothaan, 1951b). In this
way, the electron configurations of ground and excited states of molecules
are given much in the same way as those familiar for atoms. In our case of
the N ¼ 10-electron molecules H 2 O and NH 3 , the electron configurations
of their totally symmetric singlet 1 A 1 ground states are given by

1 A 1 Þ :1a 1 2a 1 1b 2 3a 1 1b 1

H 2 O ð C 2v ; ð 12 : 41 Þ

1 A 1 Þ :1a 1 2a 1 1e 4 3a 1

NH 3 ð C 3v

; ð 12 :

42 Þ