e) State Hund’s rules. Obtain the ground state terms of Li and Si.
Answers
Answer:
Hund's rules refers to a set of rules that German physicist Friedrich Hund formulated around 1927, which are used to determine the term symbol that corresponds to the ground state of a multi-electron atom.
The three rules are:[1][2][3]
1.For a given electron configuration, the term with maximum multiplicity has the lowest energy. The multiplicity is equal to {\displaystyle 2S+1\ }2S+1\ , where {\displaystyle S}S is the total spin angular momentum for all electrons. The multiplicity is also equal to the number of unpaired electrons plus one.[4] Therefore, the term with lowest energy is also the term with maximum {\displaystyle S\,} S \, and maximum number of unpaired electrons.
2.For a given multiplicity, the term with the largest value of the total orbital angular momentum quantum number {\displaystyle L\,} L \, has the lowest energy.
3.For a given term, in an atom with outermost subshell half-filled or less, the level with the lowest value of the total angular momentum quantum number {\displaystyle J\,}J\, (for the operator {\displaystyle {\boldsymbol {J}}={\boldsymbol {L}}+{\boldsymbol {S}}}{\boldsymbol {J}}={\boldsymbol {L}}+{\boldsymbol {S}}) lies lowest in energy. If the outermost shell is more than half-filled, the level with the highest value of {\displaystyle J\,}J\, is lowest in energy.