11th Class Chemistry Classification of Elements and Periodicity in Properties

  • question_answer 105)   Discuss and compare the trends in ionisation enthalpy of elements of group I with those of group 17 elements.


      The ionisation enthalpies of alkali metals are relatively low as they have large size, i.e., the outermost electron is far from the nucleus and can be easily removed. The ionisation enthalpy decreases from Li to Cs as the size increases from top to bottom. The ionisation enthalpies of halogens are very high. This indicates that the halogens have a little tendency to lose electron. This is due to high effective nuclear charge. However, the ionisation enthalpies decrease from F to I as the atomic size increases.

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