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Order of the term symbols in decreasing energy, 1d, 3f, 3p, 1s
Accepted Answer
The order of the term symbols in decreasing energy is: 3F > 3P > 1D > 1S. This order is based on Hund's rules and the relationship between the total angular momentum (L) and spin angular momentum (S) of the electrons in the atom. Here's a breakdown:
Hund's Rule 1: For a given electron configuration, the term with the highest multiplicity (2S+1) has the lowest energy. Therefore, 3F (with multiplicity 3) is higher in energy than 1D (with multiplicity 2).
Hund's Rule 2: For a given multiplicity, the term with the highest total angular momentum (L) has the lowest energy. So, within the triplet terms (3F and 3P), 3F (with L=3) has a higher energy than 3P (with L=1).
Hund's Rule 3: For a given L and S, the term with the highest J value (J = L+S for less than half-filled shells) has the lowest energy. Since we are comparing the energies of different L values, this rule is not relevant in this case.
The 1S term is lowest in energy because it has the lowest total angular momentum (L=0) and the lowest multiplicity (1).
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