Ans: option (B).
How barium has higher I.E. than potassium?
Q.19. Decreasing ionization potential for K, Ca & Ba is
(A) Ba > K > Ca
(B) Ca > Ba > K
(C) K > Ba > Ca
(D) K > Ca > Ba

Dear Student,
Let us consider the electronic configuration of cations generated after removal of one electron from each K, Ca and Ba.



Electronic Configuration
K 3s2 3p64s1
Ca 3s2 3p6 4s2
Ba 5s2 5p6 6s2
 As we can see that, K will have completely filled outermost shell after removal of one electron. Therefore, removal of the electron will require less amount of energy. Thus, among the given elements K will have the lowest ionization energy.
Among Ca and Ba, Ca will have higher ionization energy, because ionization energy decreases on moving down the group.

Thus, the correct order of increasing second ionization energy is  Ca> Ba >  K.

Hope this information will clear your doubts regarding ionization energy.

In case of any doubt, just post your query on the forum and our experts will try to help you as soon as possible.

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Because barium is in 2nd group of periodic table so it has more ionisation energy that is more energy is required to convert a neutral barium atom to a positively charged ion called cation
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@ravneet kaur....according to what u are saying barium should have greater I.E than calcium because barium is placed below calcium in periodic table...but as u can see..option b is correct answer given..so how do u justify ur explanation
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@ lakshya : give your email id bro. I will ask you some questions there!
Experts don't answer me frequently after coming to 11th.
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(Request: I have ntse stage 2 exam on may 13. So i might not be able to answer ur questions temporarily..by the way i have completed only 1 chapter in each subject)
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