. An excited helium atom has the configuration 3 d2. Use spectroscopic notation to give the terms which arise from the combinations of L and S allowed under the Pauli exclusion principle. Use Hund's rules to suggest the energy order in which these terms are likely to occur. For each term deduce the allowed values of the total angular momentum quantum number, J. Hence give the full designation of each level, including parity, using spectroscopic notation. Which level has the lowest energy?