The successive ionisation enthalpies of an element X in ( kJ mol ⁻¹ ) are 1012, 1907, 2955,4955,6275 and 21,260 respectively, the element X is

Step-by-step solution

array ll First ionisation enthalpy & 1012 ~kJ ~mol ⁻¹ Second ionisation enthalpy & 1907 ~kJ ~mol ⁻¹ Third ionisation enthalpy & 2955 ~kJ ~mol ⁻¹ Fourth ionisation enthalpy & 4955 ~kJ ~mol ⁻¹ Fifth ionisation enthalpy & 6275 ~kJ ~mol ⁻¹ Sixth ionisation enthalpy & 21,260 ~kJ ~mol ⁻¹ array Since, sixth ionisation enthalpy is much higher, it means that the removal of sixth electron is from the stable configuration, therefore the element is phosphorus ( P ) having 5 electrons in the valence shell.