Four period 4 metals have these data, listed as enthalpy of atomisation, melting point, first ionisation enthalpy and metallic radius. Ca: $178\ \text{kJ mol}^{-1}$, $1115\ \text{K}$, $590\ \text{kJ mol}^{-1}$, $197\ \text{pm}$. Cu: $338\ \text{kJ mol}^{-1}$, $1358\ \text{K}$, $745\ \text{kJ mol}^{-1}$, $128\ \text{pm}$. Zn: $131\ \text{kJ mol}^{-1}$, $693\ \text{K}$, $906\ \text{kJ mol}^{-1}$, $134\ \text{pm}$. Ga: $277\ \text{kJ mol}^{-1}$, $303\ \text{K}$, $579\ \text{kJ mol}^{-1}$, $135\ \text{pm}$. Which statement is consistent with these data and with the electronic structures of the atoms?