Solve it pls

Solve it pls Which of the following atomic species has maximum ionisation energy? (c) Se- rhe correct order of I.E. 2. is:

Dear student,

The correct option (b)  that  is S^-.

The energy ionization needed to remove an electron from a neutral atom is called ionization energy.
The more close the outermost electrons to the nucleus, more it will become difficult to remove an electron from the outermost shell.
The outermost electrons in Se^- is present in electrons in 4p orbital.
The outermost electrons in Te^- is present in electrons in 5p orbital.
The outermost electrons in S^- is present in electrons in 3p orbital.
The outermost electrons in O^- is present in electrons in 2p orbital.

The expected order of decreasing ionization energy is,
O^->S^->Se^->Te^-

but, the actual order of decreasing ionization energy is,
S^->O^->Se^->Te^-

This is because 2p orbital has smaller size and the inter electronic repulsion in compact 2p- orbitals is more than the 3p- orbitals.
Thus, the electron present in outermost shell of oxygen anion feel more repulsion in 2p- orbital than the electron present in 3p-orbital of sulphur anion, so it becomes easy to remove an electron from the outermost shell of oxygen.
Therefore, S^- has maximum ionization energy.

Regards


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