First, second and third I.P values are 100eV, 150eV and 1500eV . Element can be:

a) Be b) B c) F d) Na

The correct answer is (a) Beryllium.

From the given values of ionisation potential, we observe that the value of second ionisation potential is greater than first ionisation potential, while the third ionisation potential is very large as compared to both first and second ionisation potential. The value of third ionisation potential suggests that the third electron is being removed from a closed shell. It is the elements of group II which achieve a noble gas configuration after losing two electrons, and so the removal of third electrons from the divalent cation thus formed requires a lot of energy. Out of the given elements, it is beryllium which belong to group II. Hence, the answer is (a) Beryllium. 

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