Q. The correct order of decreasing second ionisation enthalpy of is-

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A

B

C

D

Solution:

Electronic configuration of the given elements are

In general, ionization potential ( both 1^st and 2^nd ) increases form left to right across the period due to increase in effective nuclear charge. On this basis, the second IP values should exhibit the trend :
Mn > Cr > V > Ti
But the actual observed order is :
Cr > Mn > V > Ti
Practically, only chromium is exceptional and rest others show the normal trend. This exceptional behaviour of chromium is due to the stable configuration ( 3d⁵ ) that it achieves after the loss of first electron.

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