Draw the Lewis structure of PCl5:
• P (EN = 2.1) is less electronegative than chlorine (EN = 3.0) so P is the central atom.
Group Valence Electrons
P 5A 1 × 5 e– = 5 e–
Cl 7A 5 × 7 e– = 35 e–
Total: 40 valence e–
The Lewis structure is:
The electronegativity difference between P and Cl is 0.9 so the C–Cl bond is nonpolar. Recall that dipole arrows point towards the more electronegative atom.
The molecule PCl5 is observed not to have a dipole moment. This is because:
A. There are no lone pairs of electrons on the central atom
B. As a gas and liquid PCl5 is not a ionic, but rather the bonds are covalent
C. The polarity of the P-Cl bonds cancel out due to the geometry of the molecule.
D. There are two lone pairs of electrons on the central atom, but due to the repulsion, they are on opposite sides of the central atom and cancel out.
E. P and Cl are ciose in the periodic table, so they have very similar electronegatives, and as such, the P-Cl bonds are not polar.
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