Slide 1 of 33 © Copyright Pearson Prentice Hall Polar Bonds and Molecules > 8.4 Bond Polarity D....

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© Copyright Pearson Prentice Hall

Polar Bonds and Molecules

>8.4 Bond Polarity

D. Bond Polarity & Molecules:

1. nonpolar covalent bond: the bonding electrons are shared equally

& pulls equally (as occurs when identical atoms are bonded)

2. polar covalent bond: the electrons are shared unequally, known also as a polar bond

a. more electronegative atom attracts electrons more strongly. b. less electronegative atom has a slightly positive charge

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> Polar Molecules

3. polar molecule: one end of the molecule is slightly negative and the other end is slightly positive.

a. called a dipolar molecule, or a dipole.

b. tend to become oriented with respect to the positive and negative plates.

8.4

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>8.4 Attractions Between Molecules

3. Intermolecular attractions: weaker than either ionic or covalent bonds.

a. responsible for determining whether a molecular compound is a gas, a liquid, or a solid at a given temperature.

b. Van der Waals forces: weakest forces

i. Dipole interactions occur when polar molecules are attracted to one another.

ii. Dispersion forces, the weakest forces, caused by the motion of

electrons.

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> Attractions Between Molecules

4. Hydrogen bonds: attractive forces in which a hydrogen covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom. (Water)

8.4

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> Attractions Between Molecules

The relatively strong attractive forces between water molecules cause the water to form small drops on a waxy surface.

8.4

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>8.4 Intermolecular Attractions and Molecular Properties

5. Network solids (or network crystals): solids in which all of the atoms are covalently bonded to each other.

a. melt at temperatures 1000°C or higher, or decompose without melting at all.

(Diamond is an example it vaporizes to a gas at 3500°C)

b. Melting a network solid would require breaking covalent bonds throughout the solid.

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> Intermolecular Attractions and Molecular Properties (copy table into your journal)

8.4


Slide 8 of 33

8.4 Section Quiz.

1. In a molecule, the atom with the largest electronegativity value

a. repels electrons more strongly and aquires a slightly negative charge.

b. repels electrons more strongly and aquires a slightly positive charge.

c. attracts electrons more strongly and aquires a slightly positive charge.

d. attracts electrons more strongly and aquires a slightly negative charge.


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2. When polar molecules are placed between oppositely charged plates, the negative

a. molecules stick to the positive plates.

b. molecules stick to the negative plates.

c. ends of the molecules turn toward the positive plates.

d. ends of the molecules turn toward the negative plates.

8.4 Section Quiz.


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3. Which of the following bond types is the weakest?

a. ionic bond

b. Van der Waals force

c. covalent bond

d. hydrogen bond

8.4 Section Quiz.


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> Chem ASAP

Concept Map 8 Solve the Concept Map with the help of an interactive guided tutorial.

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