Question

The second ionisation potentials in electron volts of oxygen and fluorine atoms are respectively given by:

• A. 35.1, 38.3
• B. 38.3, 38.3
• C. 38.3, 35.1
• D. 35.1, 35.1

Answer 1

Answer: (C)

38.3, 35.1

The second ionization potentials of oxygen and fluorine atoms are 38.3 eV and 35.1 eV respectively.

The electronic configuration of $O^{+}$ ion is $1s^{2}2s^{2}2p^3$ whereas that of $O^{2+}$ ion is $1s^{2}2s^{2}2p^2$.
Thus, during ionization, the stable configuration of half filled $2p$ orbital is broken. This requires high energy.

The electronic configuration of $F^{+}$ ion is $1s^{2}2s^{2}2p^4$ whereas that of $F^{2+}$ ion is $1s^{2}2s^{2}2p^3$.
Thus, during ionization, the stable configuration of half filled $2p$ orbital is formed. This requires less energy.