Calcium (ca) has an atomic number of 20. what is calcium's ground-state electron configuration? 1s21p61d101f2 1s21p62s22p63s23p2 1s22s22p63s23p64s2 1s22s22p63s23p63d2

C. 1s22s22p63s23p43d104s24p5

Answerδh > 0explanationc₆h₆  (s)  → c₆h₆ (l)if you are changing it from a solid to a liquid, you are pretty much melting the solid. this requires heat energy. therefore, the reaction is endothermic (takes in energy); the system enthalpy increases as the reaction proceeds: δh > 0.