Irodov Problem 6.121

The key is to reverse-engineer the electron configuration from the term symbol $^{2S+1}L_J$. Extract the multiplicity to find total spin $S$, use the letter to identify orbital angular momentum $L$, then apply Hund's rules (maximize $S$ first, then $L$, then determine $J$) to count electrons in the partially filled subshell. Each subshell has a maximum capacity that constrains your answer—you're looking for the unique electron count that produces exactly that term as the ground state.

The key is to reverse-engineer the electron configuration from the term symbol $^{2S+1}L_J$. Extract the multiplicity to find total spin $S$, use the letter to identify orbital angular momentum $L$, then apply Hund's rules (maximize $S$ first, then $L$, then determine $J$) to count electrons in the partially filled subshell. Each subshell has a maximum capacity that constrains your answer—you're looking for the unique electron count that produces exactly that term as the ground state.