Question

20. Explain exception in the values of ionization enthalpy for elements of second period.​

Answer 1

Answer:

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Answer 2

The exceptions in the ionization energies of elements of the second period are Be>B and N>O.

• The ionization energy of elements generally increases from left to right in a period.
• But there are some exceptions like in the case of beryllium and boron.
• Beryllium, with atomic number 4 has more ionization energy than boron with atomic number 5.
• This can be attributed to the filled orbitals on the outermost shell of beryllium, that is $1s^{2} 2s^{2}$.
• So beryllium has more ionization energy than boron.
• Similarly nitrogen has half-filled p-orbitals in the outermost shell, $1s^{2} 2s^{2} 2p^{3}$, which makes it difficult to remove an electron.
• So ionization energy of nitrogen is greater than that of oxygen.