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Ch.11 - Chemical Bonding II: Molecular Shapes, VSEPR & MO Theory
Chapter 11, Problem 50

Determine whether each molecule in Exercise 36 is polar or nonpolar. a. CF4 b. NF3 c. OF2 d. H2S

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1
Identify the molecular geometry of each molecule using the VSEPR theory. This will help in understanding the distribution of electron clouds and the overall shape of the molecule.
Determine the electronegativity of each atom in the molecules. Molecules with a significant difference in electronegativity between bonded atoms will have polar bonds.
Analyze the molecular geometry to see if the polar bonds are symmetrically arranged. If the polar bonds are symmetrically arranged, the molecule is nonpolar because the dipole moments cancel each other out.
For molecules with asymmetrically arranged polar bonds, consider the overall molecular polarity. The molecule will be polar if the dipole moments do not cancel out.
Apply these considerations to each molecule: CF<sub>4</sub>, NF<sub>3</sub>, OF<sub>2</sub>, and H<sub>2</sub>S to determine if they are polar or nonpolar.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. The shape of a molecule is determined by the number of bonding pairs and lone pairs of electrons around the central atom, which can influence the distribution of charge and ultimately the polarity of the molecule.
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Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. Differences in electronegativity between bonded atoms can lead to polar covalent bonds, where electrons are shared unequally, creating a dipole moment that contributes to the overall polarity of the molecule.
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Dipole Moment

A dipole moment is a vector quantity that represents the separation of positive and negative charges in a molecule. Molecules with a net dipole moment are considered polar, while those with symmetrical charge distribution and no net dipole moment are nonpolar. The presence of polar bonds and the molecular geometry together determine the overall polarity.
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