Question

Follow the directions in Question 27 for (a) oxygen in HOF (b) nitrogen in \(\mathrm{NO}_{2}\) - (c) phosphorus in \(\mathrm{PCl}_{1}\)

Short answer

Answer: The molecular shape of HOF and \(\mathrm{NO}_{2}\) is bent, while \(\mathrm{PCl}_{3}\) has a trigonal pyramidal shape. All three molecules are polar.

Step-by-step solution

Identify Central Atom

For each molecule, we need to identify the central atom. The central atom is generally the least electronegative element, excluding hydrogen. (a) HOF: Oxygen is the least electronegative element (excluding hydrogen), so it will be the central atom. (b) \(\mathrm{NO}_{2}\): Nitrogen is least electronegative, thus it will be the central atom. (c) \(\mathrm{PCl}_{3}\): Phosphorus is the least electronegative element, so it will act as the central atom.

Determine Bond Angles and Molecular Shape

Next, we will determine the bond angles and molecular shape of each molecule using the VSEPR (Valence Shell Electron Pair Repulsion) theory. (a) HOF: - Oxygen has 6 valence electrons, 1 electron for bonding with hydrogen and 1 for bonding with fluorine, and 4 electrons in non-bonding pairs, which results in 2 lone pairs. - The electronic geometry is tetrahedral. - The molecular shape is bent, with a bond angle of about 104.5°. (b) \(\mathrm{NO}_{2}\): - Nitrogen has 5 valence electrons, with 1 unpaired electron and 2 electrons participating in double bonds with both oxygen atoms. - The electronic geometry is trigonal planar. - The molecular shape is bent, with a bond angle of about 120°. (c) \(\mathrm{PCl}_{3}\): - Phosphorus has 5 valence electrons, with 3 electrons participating in bonds with the chlorine atoms. - The electronic geometry is tetrahedral. - The molecular shape is trigonal pyramidal, with a bond angle of about 107.3°.

Identify Polarity

Now, we will determine the polarity of each molecule by considering the electronegativity difference between the atoms and the molecular shape. (a) HOF: - Electronegativity difference between H-O and O-F bonds generates a dipole moment. - The bent molecular shape does not cancel out the dipole moment, making HOF a polar molecule. (b) \(\mathrm{NO}_{2}\): - Electronegativity difference between nitrogen and oxygen atoms generates a dipole moment. - The bent molecular shape does not cancel out the dipole moment, making \(\mathrm{NO}_{2}\) a polar molecule. (c) \(\mathrm{PCl}_{3}\): - Electronegativity difference between phosphorus and chlorine atoms generates a dipole moment. - The trigonal pyramidal molecular shape does not cancel out the dipole moment, making \(\mathrm{PCl}_{3}\) a polar molecule. In summary, all three molecules (HOF, \(\mathrm{NO}_{2}\), and \(\mathrm{PCl}_{3}\)) are polar, with HOF and \(\mathrm{NO}_{2}\) having a bent molecular shape, and \(\mathrm{PCl}_{3}\) adopting the trigonal pyramidal shape.