Question

The oxyanion of nitrogen in which it has the highest oxidation state is the nitrate ion $\left(N{O^{-}}_3\right)$. The corresponding oxyanion of phosphorus is$P{O}_4^{3-}$ . The$N{O}_4^{3-}$ ion is known but is not very stable. The $P{O}_4^{3-}$ ion is not known. Account for these differences in terms of the bonding in the four anions.

Short answer

Nitrogen is unable to hold four oxygen atoms. The bond is insecure.

Step-by-step solution

Define anion and cation

Cations are ions with a positive charge (atoms or groups of atoms that have more protons than electrons due to having lost one or more electrons). Anions are ions with a negative charge (meaning they have more electrons than protons due to having gained one or more electrons).

The highest oxidation state is in $\left(N{O^{-}}_3\right)$ is known but not stable and the oxyanion of phosphorus is$P{O}_4^{3-}$ is not known.

Stability of  PO43-  and  NO43-

The anions $P{O}_4^{3-}$ and $N{O}_4^{3-}$ have a similar lewis structure because they have 32 valence electrons .

The nitrogen atom in $N{O}_4^{3-}$ are in tetrahedral arrangement .

Because nitrogen is smaller than phosphorus, it is unlikely that all four oxygen atoms will fit around it.

On oxygen, the lone pairs resist each other.

Because nitrogen has a smaller atomic radius, forming $\text{N}{{\text{O}}_4}^{3-}$ would be too crowded.

Because phosphorus has a greater atomic radius, the bond lengths can accommodate the lone pairs because they are wider apart.

As a result, $\text{P}{{\text{O}}_4}^{3-}$ is stable, whereas $\text{N}{{\text{O}}_4}^{3-}$is unstable.

Describe bonding in the anions

The anions $P{O}_4^{3-}$ and $N{O}_3^{-}$ have a similar lewis structure because they have 24 valence electrons .

The Lewis-structure of $N{O}_3^{-}$ has an electronic structure with one $\text{N}=\text{O}$bond, which is relatively stable since the pi-pi orbitals overlap quite well in period 2.

Because the atoms in period 3 are larger, these elements do not form strong double bonds; the $\text{P}=\text{O}$ structure, which is similar to that of ${\text{NO}}_3-$, is weak or non-existent because the pi-pi interaction is weak.

Because $\text{P}=\text{O}$ bonds are not especially stable, whereas $\text{N}=\text{O}$ bonds are stable,${\text{PO}}_3-$ is an unstable species.

Nitrogen is unable to hold four oxygen atoms. The bond ${\text{PO}}_3-$ is insecure.