Chapter 5

What is electronegativity? What are the periodic trends in electronegativity?

Explain the difference between a pure covalent bond, a polar covalent bond, and an ionic bond.

What is meant by the percent ionic character of a bond? Do any bonds have 100% ionic character?

How do you determine the number of electrons that go into the Lewis structure of a molecule? A polyatomic ion?

What are resonance structures? What is a resonance hybrid?

Do resonance structures always contribute equally to the overall structure of a molecule? Explain.

What is formal charge? How is formal charge calculated? How is it helpful?

Why does the octet rule have exceptions? Give the three major categories of exceptions and an example of each.

Give some examples of some typical bond lengths. Which factors influence bond lengths?

According to VSEPR theory, what determines the geometry of a molecule?

Name and draw the five basic electron geometries, and state the number of electron groups corresponding to each. What constitutes an electron group?

Explain the difference between electron geometry and molecular geometry. Under what circumstances are they not the same?

List the correct electron and molecular geometries that correspond to each set of electron groups around the central atom of a molecule. a. four electron groups overall; three bonding groups and one lone pair b. four electron groups overall; two bonding groups and two lone pairs c. five electron groups overall; four bonding groups and one lone pair d. five electron groups overall; three bonding groups and two lone pairs e. five electron groups overall; two bonding groups and three lone pairs f. six electron groups overall; five bonding groups and one lone pair g. six electron groups overall; four bonding groups and two lone pairs

Determine if a bond between each pair of atoms would be pure covalent, polar covalent, or ionic. a. Br and Br b. C and Cl c. C and S d. Sr and O

Determine if a bond between each pair of atoms would be pure covalent, polar covalent, or ionic. a. C and N b. N and S c. K and F d. N and N

Write the Lewis structure for each molecule. a. PH3 b. SCl2 c. HI d. CH4

Write the Lewis structure for each molecule. a. NF3 b. HBr c. SBr2 d. CCl4

Write the Lewis structure for each molecule. a. SF2 b. SiH4 c. HCOOH (both O bonded to C) d. CH3SH (C and S central)

Write the Lewis structure for each molecule. a. CH2O b. C2Cl4

Write the Lewis structure for each molecule or ion. a. CI4 b. N2O c. SiH4 d. Cl2CO

Write the Lewis structure for each molecule or ion. a. H3COH b. OH- c. BrO- d. O2 2-

Write the Lewis structure for each molecule or ion. a. N2H2 b. N2H4 c. C2H2 d. C2H4

Write the Lewis structure for each molecule or ion. a. H3COCH3 b. CN- c. NO2- d. ClO-

Write a Lewis structure that obeys the octet rule for each molecule or ion. Include resonance structures if necessary and assign formal charges to each atom. a. SeO2 b. CO3 2- c. ClO- d. NO2-

Write a Lewis structure that obeys the octet rule for each ion. Include resonance structures if necessary and assign formal charges to each atom. a. ClO3- b. ClO4- c. NO3- d. NH4+

Draw the Lewis structure (including resonance structures) for the acetate ion (CH3COO-). For each resonance structure, assign formal charges to all atoms that have formal charge.

Draw the Lewis structure (including resonance structures) for methyl azide (CH3N3). For each resonance structure, assign formal charges to all atoms that have formal charge.

Write the Lewis structure for each molecule (octet rule not followed). a. BCl3 b. NO2 c. BH3

Write the Lewis structure for each molecule (octet rule not followed). a. BBr3 b. NO c. ClO2

Write the Lewis structure for each ion. Include resonance structures if necessary and assign formal charges to all atoms. If necessary, expand the octet on the central atom to lower formal charge. a. PO4 3- b. CN- c. SO3 2- d. ClO2-

Write Lewis structures for each molecule or ion. Include resonance structures if necessary and assign formal charges to all atoms. If you need to, expand the octet on the central atom to lower formal charge. a. SO4 2- b. HSO4 - c. SO3 d. BrO2 -

Write Lewis structures for each molecule or ion. Use expanded octets as necessary. a. PF5 b. I3 - c. SF4 d. GeF4

Write Lewis structures for each molecule or ion. Use expanded octets as necessary. a. ClF5 b. AsF6 - c. Cl3PO d. IF5

A molecule with the formula AB3 has a trigonal pyramidal geometry. How many electron groups are on the central atom (A)?

A molecule with the formula AB3 has a trigonal planar geometry. How many electron groups are on the central atom?

Determine the electron geometry, molecular geometry, and idealized bond angles for each molecule. In which cases do you expect deviations from the idealized bond angle? a. PF3 b. SBr2 c. CHCl3 d. CS2

Which species has the smaller bond angle, H3O+ or H2O? Explain.

Which species has the smaller bond angle, ClO4 - or ClO3 -? Explain.

Determine the molecular geometry about each interior atom and draw each molecule. (Skeletal structure is indicated in parentheses.) a. C2H2 (HCCH) b. C2H4 (H2CCH2) c. C2H6 (H3CCH3)

Determine the geometry about each interior atom in each molecule and draw the molecule. (Skeletal structure is indicated in parentheses.) a. CH3OH (H3COH) b. CH3OCH3 (H3COCH3) c. H2O2 (HOOH)

Determine the geometry about each interior atom in each molecule and draw the molecule. (Skeletal structure is indicated in parentheses.) a. CH3NH2 (H3CNH2) b. CH3CO2CH3 (H3CCOOCH3 both O atoms attached to second C) c. NH2CO2H (H2NCOOH both O atoms attached to C)

Explain why CO2 and CCl4 are both nonpolar, even though they contain polar bonds.

CH3F is a polar molecule, even though the tetrahedral geometry often leads to nonpolar molecules. Explain.

Determine whether each molecule is polar or nonpolar. a. SiCl4 b. CF2Cl2 c. SeF6 d. IF5

Amino acids are the building blocks of proteins. The simplest amino acid is glycine (H2NCH2COOH). Draw a Lewis structure for glycine. (Hint: The central atoms in the skeletal structure are nitrogen bonded to carbon, which is bonded to another carbon. The two oxygen atoms are bonded directly to the rightmost carbon atom.)

Formic acid is partly responsible for the sting of ant bites. By mass, formic acid is 26.10% C, 4.38% H, and 69.52% O. The molar mass of formic acid is 46.02 g>mol. Find the molecular formula of formic acid and draw its Lewis structure.

Diazomethane is a highly poisonous, explosive compound because it readily evolves N2. Diazomethane has the following composition by mass: 28.57% C; 4.80% H; and 66.64% N. The molar mass of diazomethane is 42.04 g>mol. Find the molecular formula of diazomethane, draw its Lewis structure, and assign formal charges to each atom. Why is diazomethane not very stable? Explain.

Draw the Lewis structure for nitric acid (the hydrogen atom is attached to one of the oxygen atoms). Include all three resonance structures by alternating the double bond among the three oxygen atoms. Use formal charge to determine which of the resonance structures is most important to the structure of nitric acid.

Draw the Lewis structure for each organic compound from its condensed structural formula. a. C3H8 b. CH3OCH3 c. CH3COCH3 d. CH3COOH e. CH3CHO

Draw the Lewis structure for each organic compound from its condensed structural formula. a. C2H4 b. CH3NH2 c. HCHO d. CH3CH2OH e. HCOOH