The enthalpy of atomisation is 397 kJ/mol for chromium, with a molar mass of 52.0 g/mol, and 126…

The nuclear charge rises by one at each step of a series, but a new $3d$ electron screens the $4s$ electrons by about $0.85$, so $Z_{eff}$ rises slowly. Metal bonds are strong where many d electrons can bond. Enthalpy of atomisation, $\Delta_a H$, is the energy to turn one mole of solid metal into gaseous atoms. The energy to reach $\text{M}^{2+}(g)$ is $\Delta_a H + \Delta_i H_1 + \Delta_i H_2$, and hydration returns part of it.