Ground state term symbol
        Selected based on Hund's Rule

def ground_state_term_symbol(self):
        """
        Ground state term symbol
        Selected based on Hund's Rule

        """
        L_symbols = 'SPDFGHIKLMNOQRTUVWXYZ'

        term_symbols = self.term_symbols
        term_symbol_flat = {term: {"multiplicity": int(term[0]),
                                   "L": L_symbols.index(term[1]),
                                   "J": float(term[2:])}
                            for term in sum(term_symbols, [])}

        multi = [int(item['multiplicity'])
                 for terms, item in term_symbol_flat.items()]
        max_multi_terms = {symbol: item
                           for symbol, item in term_symbol_flat.items()
                           if item['multiplicity'] == max(multi)}

        Ls = [item['L'] for terms, item in max_multi_terms.items()]
        max_L_terms = {symbol: item
                       for symbol, item in term_symbol_flat.items()
                       if item['L'] == max(Ls)}

        J_sorted_terms = sorted(max_L_terms.items(),
                                key=lambda k: k[1]['J'])
        L, v_e = self.valence
        if v_e <= (2 * L + 1):
            return J_sorted_terms[0][0]
        else:
            return J_sorted_terms[-1][0]