What is the correct dipole moment of NH3 and NF3 respectively?

(A)- 4.90×10^-30 C m and 0.80×10^-30 C m

(B)- 0.80×10^-30 C m and 4.90×10^-30 C m

(C)- 4.90×10^-30 C m and 4.90×10^-30 C m

(D)- 0.80×10^-30 C m and 0.80×10^-30 C m

To determine the correct dipole moments of ammonia (NH3) and nitrogen trifluoride (NF3), we need to consider their molecular structures and the electronegativity of the atoms involved. Dipole moment is a vector quantity that reflects the separation of positive and negative charges in a molecule, and it is influenced by both the bond polarity and the molecular geometry.

Understanding Dipole Moments

The dipole moment (μ) is calculated using the formula:

μ = q × r

where q is the charge and r is the distance between the charges. In molecules, the dipole moment is affected by the arrangement of polar bonds and the overall shape of the molecule.

Analyzing NH3

Ammonia (NH3) has a trigonal pyramidal shape due to the presence of a lone pair on the nitrogen atom. The nitrogen atom is more electronegative than hydrogen, creating polar N-H bonds. The dipole moments of these bonds add up vectorially, resulting in a net dipole moment for the molecule.

The dipole moment of NH3 is approximately 4.90 × 10^-30 C m. This relatively high value is due to the significant electronegativity difference between nitrogen and hydrogen, combined with the molecular geometry that does not allow the dipoles to cancel out.

Examining NF3

Nitrogen trifluoride (NF3) also has a trigonal pyramidal shape, similar to NH3. However, the electronegativity of fluorine is much higher than that of nitrogen, resulting in highly polar N-F bonds. Despite this, the dipole moments of the N-F bonds point towards the fluorine atoms, which somewhat cancels out the overall dipole moment due to the geometry of the molecule.

The dipole moment of NF3 is significantly lower, approximately 0.80 × 10^-30 C m. This is because the vector sum of the dipole moments in NF3 does not lead to a strong net dipole, as the bond dipoles are oriented in a way that reduces the overall dipole moment.

Final Comparison

Now that we have the dipole moments for both molecules:

• NH3: 4.90 × 10^-30 C m
• NF3: 0.80 × 10^-30 C m

Based on this analysis, the correct answer to your question is option (A) - 4.90 × 10^-30 C m for NH3 and 0.80 × 10^-30 C m for NF3.