Question

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

Answer 1

NF5. Is most stable. So I think . Because of compete octet. 3 +5=8

Answer 2

Answer: The correct answer is $NF_5$ molecule.

Explanation:

The electronic configuration of nitrogen atom is $1s^22s^22p^3$

Number of valence electrons of this element are 5.

To know the stability, we need to find out the hybridization of central metal in each compound. Hybridization is calculated using the Lewis 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 $sp^3d$. It is visible that the nitrogen atom does not have any d-orbitals, therefore this hybridization is not possible and hence, this compound is not possible. 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 = 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 present in the compound.

Thus, the unstable molecule is $NF_5$

The lewis dot structures of all the molecules is attached in the image below.