Question

The correct order of ionization energies of $F^{-},C{l}^{-}F$ and $Cl$ is:

• A. $Cl<F<C{l}^{-}<F^{-}$
• B. $C{l}^{-}<F^{-}<Cl<F$
• C. $F^{-}<C{l}^{-}<Cl<F$
• D. $C{l}^{-}<Cl<F^{-}<F$

Answer 1

Answer: (C)

$F^{-}<C{l}^{-}<Cl<F$

The correct order of ionization energies of $F^{-},C{l}^{-},F$ and $Cl$ is $F^{-}<C{l}^{-}<Cl<F$.

$C{l}^{-}>F^{-}$ because the size of F is less than $C{l}^{-}$, so the ionization potential will be more for F than $C{l}^{-}$.

$F>Cl$ because the size of F is less than Cl,so the ionization potential will be more for F than Cl.

In a group, the ionization energy decreases from top to bottom.
The size of the anion is greater than the size of the neutral atom. Due to this, the attraction of the nucleus for the valence electrons is larger in case of neutral atom. Hence, the ionization energy of the neutral atom is larger than that of anion. In case of halogens, the addition of an electron leads to breaking of the noble gas configuration. The ionization energy of fluoride ion is lowest due to electron electron repulsion.