Three elements chromium, manganese and iron have heat of atomizations 400 kJ, 420 kJ and 280 kJ per 1 mole of metal but not respectively. Arrange the values in the order for chromium, manganese and iron in kJ/mol.

Both chromium and manganese have stable d⁵ configuration and the d-orbitals are reluctant to participate the d⁵ configuration is more stable since in chromium d⁵ configuration is anomalous. So manganese has low heat of atomization than chromium. In iron having d⁶ configuration the 4 unpaired electrons can participate in bonding effecting. So iron has more heat of atomization than chromium and manganese