Question

Which one is not stable and why?
NF3, NF5, HNO3, NO, N2O5

Answer 1

NF3 is not sutable for this

Answer 2

Answer:

The unstable molecule is $NF_5$

Explanation:

The electronic configuration of nitrogen atom is gives as

$[N]=1s^22s^22p^3$

Number of valence electrons in nitrogen are 5.

To know the stability, we need to find out the hybridization of each compound.

Hybridization is determined by using the Lewis electron dot structures of all the compounds.

Formula used to calculate the number of atomic orbitals around central metal atom is:

Number of atomic orbitals around central metal atom = Number of bond pairs + Number of lone pairs

Bond pairs for a double bond and triple bond is taken as 1 only.

Hybridization of nitrogen in $NF_3$

Number of bond pairs = 3

Number of lone pairs = 1

Number of atomic orbitals around Nitrogen atom = 3 + 1 = 4

So, hybridization will be $sp^3$

Hybridization of nitrogen in $NF_5$

Number of bond pairs = 5

Number of lone pairs = 0

Number of atomic orbitals around Nitrogen atom = 5 + 0 = 5

So, hybridization will be $sp^3d$. As we know in nitrogen atom d-orbitals is absent.Therefore this hybridization is not possible and hence, this compound is not feasible to form. Thus, it is an unstable molecule.

Hybridization of nitrogen in $HNO_3$

Number of bond pairs = 3

Number of lone pairs = 0

Number of atomic orbitals around Nitrogen atom = 3 + 0 = 3

So, hybridization will be $sp^2$

Hybridization of nitrogen in $NO$

Number of bond pairs = 1

Number of lone pairs = 1

Number of atomic orbitals around Nitrogen atom = 1 + 1 = 2

So, hybridization will be $sp$

Hybridization of nitrogen in $N_2O_5$

Number of bond pairs = 3

Number of lone pairs = 0

Number of atomic orbitals around Nitrogen atom = 3 + 0 = 3

So, hybridization will be $sp^2$ and it will be same for both the nitrogen atoms present in the compound.

Thus, the unstable molecule is $NF_5$