How to Complete the Following for PF3: Lewis Dot Structure, Bonding, Shape, and Polarity

a. Draw the Lewis Dot Structure:

To draw the Lewis dot structure for PF₃ (phosphorus trifluoride), follow these steps:

1. Count the total number of valence electrons: Phosphorus (P) has 5 valence electrons, and each fluorine (F) atom has 7 valence electrons. So, the total is 5 + (3 × 7) = 26 valence electrons.
2. Place the least electronegative atom (P) in the center and arrange the fluorine atoms around it.
3. Connect the central atom (P) to each fluorine atom with a single bond, using 2 electrons per bond. This uses up 6 electrons (3 bonds × 2 electrons).
4. Distribute the remaining 20 electrons as lone pairs around the fluorine atoms, ensuring each fluorine has 8 electrons (including the bonding electrons).
5. Place any remaining electrons on the central phosphorus atom. In this case, phosphorus will have one lone pair.

b. Draw a Second Structure with Bonds Drawn:

In the second structure, represent the bonds as lines instead of dots. The central phosphorus atom will have three single bonds to the fluorine atoms, and one lone pair of electrons on the phosphorus.

c. Tell the Shape Using VSEPR Theory:

Using the Valence Shell Electron Pair Repulsion (VSEPR) theory, we determine the shape of PF₃:

1. Count the total number of electron pairs around the central atom: 3 bonding pairs and 1 lone pair.
2. The electron pairs will arrange themselves to minimize repulsion. The lone pair will occupy more space than the bonding pairs.
3. This arrangement results in a trigonal pyramidal shape, where the three fluorine atoms form the base of the pyramid, and the lone pair occupies the apex.

d. Tell if the Molecule is Polar or Nonpolar:

PF₃ is a polar molecule. The reason is:

1. The molecule has a trigonal pyramidal shape due to the lone pair on phosphorus.
2. The fluorine atoms are more electronegative than phosphorus, creating a dipole moment.
3. The lone pair on phosphorus further distorts the shape, making the molecule asymmetrical.
4. As a result, the dipole moments do not cancel out, and the molecule has a net dipole moment, making it polar.