Question

which compound is not stable NF3 NF5 HNO3 NO N2O5 and why

Answer 1

NO because it has a lone pair of electron and hence easily forms NO2

Answer 2

Answer: The correct answer is $NF_5$

Explanation:

The electronic configuration of nitrogen is $1s^22s^22p^3$ and number of valence electrons around this element are 5.

To check the stability of the molecules, we first need to find the hybridization around central metal atom of each molecule. Hybridization is calculated using the Lewis dot structures of all the molecules.

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, nitrogen does not have any d-orbitals, therefore this hybridization is not possible and hence, this compound is not possible. Thus, it is considered as 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 = 0

Number of atomic orbitals around Nitrogen atom = 1 + 0 = 1

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.

Thus, the unstable molecule is $NF_5$