Explain the deviation in ionisation enthalpy of some elements from the general trend by using Fig. 3.2.



The ionisation enthalpy of elements varies across period and group. The ionisation enthalpy decreases down a group and increases as we move from left to right in a period. It is affected by the following parameters.


• Effective nuclear charge on the outermost electrons.


• Electron- electron repulsion force.


• Stability of the element due to half-filled and fully filled orbitals.


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