Unit Exam Study Guide: Bonding
Topics Covered:
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The three types of Intramolecular Bonds are: Ionic, Covalent, and Metallic
o Know the differences between the three.
o Know what bond forms a crystal lattice (electrostatic lattice)
Valence Electrons
o Know what they are and how to find the number of valence electrons in
an element.
Lewis Dot Structures
o Know how to draw them
o Know what lone pairs are and what bonded pairs are
o Know the difference between a single, double, and triple bond
o Know why atoms combine to form molecules
Polarity
o Know how to determine if a binary (2 atom molecule) is polar or nonpolar
o Know how to determine if a compound consisting of more than 2 atoms
is polar or nonpolar
o Know the definition and trend in electronegativity
o Be able to draw the partial positive and partial negative ends on a
molecule if it is polar
o Know the difference between polar and nonpolar covalent compounds
Molecular Shape
o Know how to determine the shape of a compound
Intermolecular Forces
o Know the difference between intermolecular and intramolecular forces.
Which is stronger?
o Be able to tell which of the 3 intermolecular forces is the strongest and
which is the weakest
o Be able to determine the type of intermolecular force that acts on any
given molecule or compound
o Be able to explain why water has such a high boiling point and why
hexane has such a low boiling point. Why is hexane so volatile? (Hint:
we did this in the lab)
Biochemistry
o Be able to differentiate between a monomer and a polymer.
Practice Problems:
1. (a). Compare the boiling and melting point of ionic compounds to the boiling and melting
point of covalent compounds.
Ionic compounds: High boiling and melting point due to the formation of crystal lattice.
Ionic bonds are strong bonds.
Covalent compounds: Low boiling and melting point. Intermolecular forces are relatively
weak compared to electrostatic attraction between cations and anions.
(b). Based on your answer to part A, explain why CH4is a gas a room temperature.
CH4 (methane) is a nonpolar covalent compound. Therefore, only Van der Waals forces
are present. This is a very weak intermolecular force so the molecules aren't held very
tightly.
2. What happens to the electrons in an ionic, covalent, and metallic bond?
Ionic: electrons are transferred from metal to nonmetal
Covalent: electrons are shared between two nonmetals
Metallic: There is a delocalization of electrons
3. Sodium chloride, NaCl, forms a crystal lattice. Draw a picture to show what this looks like.
Na+
Cl-
Na+
Cl-
Na+
Cl-
Cl-
Na+
Na+
4. How many valence electrons do the halogens have?
7
5. Draw the Lewis Dot Structure for the following compounds:
a. CCl4
b. CH3OH
c. CH2Cl2
d. N2
N
N
e.
Typo, skip this problem
6. Which compound in problem 5 has a lone pair of electrons around the central atom?
None
7. Circle the compound(s) in problem 5 that has all single bonds. Underline the compound(s)
that have double bonds. Double underline the compounds that have a triple bond.
a, b, c are compounds that contain only single bonds. d contains a triple bond.
8. Determine whether the following is polar or nonpolar and explain how you know:
a. H2
Nonpolar; difference in EN is 0.
b. HBr
Polar; find the difference in EN
c. CH4
Nonpolar; no lone pairs, all atoms surrounding the central atom are the same,
symmetrical
d. CH2Cl2
Polar; atoms surrounding the central atom are different.
e. CCl4
Nonpolar; no lone pairs, all atoms surrounding the central are the same,
symmetrical
9. Determine the shape of NH3.
Trigonal pyrimidal
10. What are the three types of intramolecular forces and what are the three types of
intermolecular forces? Are intramolecular or intermolecular forces stronger?
Intramolecular: Covalent, Ionic, and metallic bonds
Intermolecular: Van der Waals, dipole-dipole, hydrogen bonding
All intramolecular forces are stronger than intermolecular
11. Label the three types of intermolecular forces from strongest to weakest.
Strongest ----------------------------------------->Weakest
Hydrogen bonding, dipole-dipole, Van der Waals
12. Explain in words how to determine what type of intermolecular forces are present in a
compound.
First, determine if the molecule or compound is polar. If it is not polar, Van der Waals
forces are present. If it is polar, it is dipole-dipole. If it is polar and has H bonded to
either F, O, or N, then it is hydrogen bonding.
13. What type of intermolecular force is present in the following:
a. dipole dipole
b. Van der Waals
c. Hydrogen bonding d.Van der Waals
e.Hydrogen bonding
f. dipole-dipole
14. What is the difference between a monomer and polymer. Provide one example of a
monomer that makes up a polymer.
Monomers are single subunits that make up polymers. Polymers are long chains of repeating
subunits (monomers). Amino acids are monomers that form protein (polymer).