chemical bonding.....aim 2

what is molecular polarity?

.....aim 1

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aim 3.....

 

HW From textbook “CHEMISTRY a Contemporary Approach”

 

The distribution of charge within a molecule indicates if the molecule is polar or nonpolar

 

A molecule is nonpolar when there is even distribution of charge creating symmetry.

Example 1: CO2 and CH4

 

           

Example 2: H2 ,O2, and N2 

 

       

A molecule is polar when there is uneven distribution of charge creating asymmetry.

Example:  HCl, NH3, and H2O. 

 

             

Note: The shape of the water molecule is said to be "bent"

 

Intermolecular forces are electrostatic attractions formed between opposite charge among molecules.

 

Hydrogen bonding is an example of a strong intermolecular force.

Example 1: H2O

                                    

Example 2: H2S

                                    

Since the difference in electronegativity between O and H is higher than in S and H it follows that the intermolecular force is stronger for H2O than H2S. Therefore, H2O has a higher boiling point than H2S.

 

TEST YOUR UNDERSTANDING

1/07

29 Which compound has hydrogen bonding between its molecules?

65 Explain, in terms of molecular structure or distribution of charge, why a molecule of methane (CH4) is nonpolar.

6/06

11 Which formula represents a nonpolar molecule?     (1) CH4     (2) HCl     (3) H2O     (4) NH3

8/06

10 Which formula represents a nonpolar molecule containing polar covalent bonds?    (1) H2O (2) CCl4 (3) NH3 (4) H2

11 The degree of polarity of a chemical bond in a molecule of a compound can be predicted by determining the difference in the

        (1) melting points of the elements in the compound      (2) densities of the elements in the compound

        (3) electronegativities of the bonded atoms in a molecule of the compound      (4) atomic masses of the bonded atoms in a molecule of the compound

1/05

12 Which formula represents a nonpolar molecule? (1) HCl (2) H2O (3) NH3 (4) CF4

Base your answers to questions 51 through 52 on your knowledge of chemical bonding and on the Lewis electron-dot diagrams of H2S, CO2, and F2 below.

51 Which atom, when bonded as shown, has the same electron configuration as an atom of argon?

52 Explain, in terms of structure and/or distribution of charge, why CO2 is a nonpolar molecule.

1/04

10 Which molecule is nonpolar? (1) H2O (2) NH3 (3) CO (4) CO2

20 Which of the following compounds has the highest boiling point? (1) H2O (2) H2S (3) H2Se (4) H2Te

6/04

10 Which type of molecule is CF4?
    (1) polar, with a symmetrical distribution of charge (3) nonpolar, with a symmetrical distribution of charge

    (2) polar, with an asymmetrical distribution of charge (4) nonpolar, with an asymmetrical distribution of charge

8/04

16 Molecules in a sample of NH3(l) are held closely together by intermolecular forces

                (1) existing between ions                                                    (2) existing between electrons

                (3) caused by different numbers of neutrons                  (4) caused by unequal charge distribution

41 Based on intermolecular forces, which of these substances would have the highest boiling point?  (1) He (2) O2 (3) CH4 (4) NH3

1/03

45 Each molecule listed below is formed by sharing electrons between atoms when the atoms within the molecule are bonded together.

Molecule A: Cl2         Molecule B: CCl4         Molecule C: NH3

        1. Draw the electron-dot (Lewis) structure for the NH3 molecule.

        2. Explain why CC14 is classified as a nonpolar molecule.

        3. Explain why NH3, has stronger intermolecular forces of attraction than Cl2

        4. Explain how the bonding in KCl is different from the bonding in molecules A, B, and C.

8/03

15 Which of these substances has the strongest intermolecular forces? (1) H2O 3) H2Se  (2) H2S ( (4) H2Te

6/02

The strongest forces of attraction occur between molecules of   (1) HCl              (2) HF         (3) HBr               (4) HI

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