Question

second Ip of lanthanum is most likely to second IP of which element 1) Be 2) Ca 3) Ca 4) Zn How its answer is 3 ??? Explain it with detail....

Answer 1

Second ionisation energy is defined by the equation:





It is the energy needed to remove a second electron from each ion in 1 mole of gaseous 1+ ions to give gaseous 2+ ions.
When the first electron is removed from an element,its effective nuclear charge increases. Once,the effective nuclear charge increases,the hold of nucleus over its outermost electrons increases.  So,due to the increase in effective nuclear charge,more energy is required to remove the second electron from the element.