Question

Explain the following giving an appropriate reason in each case.
(i) ${{\text{O}}_{\text{2}}}$ and ${{\text{F}}_{\text{2}}}$ both stabilize higher oxidation states of metals but ${{\text{O}}_{\text{2}}}$ exceeds ${{\text{F}}_{\text{2}}}$ in doing so.
(ii) Structures of xenon fluorides cannot be explained by valence bond approaches.

Answer 1

The electronic configuration of oxygen is $1{s^2}2{s^2}2{p^4}$. The charge on an oxygen atom is $- {\text{2}}$. The electronic configuration of fluorine is $1{s^2}2{s^2}2{p^5}$. The charge on a fluorine atom is $- {\text{1}}$. Xenon has fully filled electronic configuration.

Complete Step by step answer: (i)The metal atom is always electropositive i.e. it has a metal ion always has a positive charge over it.
The electronic configuration of oxygen is $1{s^2}2{s^2}2{p^4}$.
The electronic configuration of fluorine is $1{s^2}2{s^2}2{p^5}$.
Each oxygen atom has a charge of $- {\text{2}}$. And each fluorine atom has a charge of $- {\text{1}}$.
Thus, the charge on ${{\text{O}}_{\text{2}}}$ is higher than that on ${{\text{F}}_{\text{2}}}$.
As the charge increases the force of attraction increases.
Due to this, the force of attraction between the metal atom and ${{\text{O}}^{2 - }}$ ion is greater than that in between the meta and ${{\text{F}}^ - }$ ion.
Thus, oxygen can form multiple bonds with the metal but fluorine cannot form multiple bonds.
Thus, ${{\text{O}}_{\text{2}}}$ stabilizes higher oxidation states of metals than ${{\text{F}}_{\text{2}}}$.

(ii)According to the valence bond theory, the covalent bonds are formed by the over-lapping of the atomic orbitals that are half-filled and only unpaired electrons in the valence shell can participate in the formation of the covalent bond.
Xenon has a fully filled valence shell i.e. it has a fully filled valence electronic configuration and thus, it has no unpaired electrons.
Due to these reasons, the valence bond theory cannot explain the structures of xenon fluorides.
Thus, structures of xenon fluorides cannot be explained by valence bond approaches.

Note: The structures of xenon fluorides can be explained very well by the valence shell electron pair repulsion (VSEPR) theory and the hybridisation concept. The examples of xenon fluorides are xenon difluoride, xenon tetrafluoride, xenon hexafluoride.