Multiple Choice
Which of the following is a correct Lewis dot structure for hydrogen cyanide (HCN)?
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11. Bonding & Molecular Structure
Lewis Dot Structures: Neutral Compounds
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After drawing the Lewis structure of PBr3, determine whether the molecule is polar or nonpolar.
A
Polar
B
Nonpolar
Verified step by step guidance1
Draw the Lewis structure of PBr\_3 by first counting the total valence electrons: phosphorus (P) has 5 valence electrons, and each bromine (Br) has 7 valence electrons, so total electrons = 5 + 3 \times 7 = 26 electrons.
Arrange the atoms with phosphorus as the central atom bonded to three bromine atoms. Use pairs of electrons to form single bonds between P and each Br, then distribute the remaining electrons to satisfy the octet rule for each atom.
Determine the molecular geometry using VSEPR theory. Phosphorus with three bonded atoms and one lone pair corresponds to a trigonal pyramidal shape.
Analyze the symmetry and dipole moments: the trigonal pyramidal shape is asymmetrical, and since P and Br have different electronegativities, the bond dipoles do not cancel out.
Conclude that because of the asymmetrical shape and the presence of polar P-Br bonds, the molecule has a net dipole moment and is therefore polar.
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