Chemistry Chapter 8 Review
8.1
Topics: Molecules and Molecular Compounds
Question: How are the melting points and boiling points of molecular compounds
different from those of Ionic compounds?
Answer: Molecular compounds tend to have relatively lower boiling and melting
points than Ionic compounds.
Question: What information does a molecular formula provide?
Answer: It shows how many atoms of each element a molecule contains.
Vocabulary:
Covalent Bond – Atoms held together by sharing electrons.
Molecule – A neutral group of atoms joined together by Covalent Bonds.
Diatomic Molecule – A molecule consisting of two atoms.
Molecular Compound – A compound that is composed of molecules.
Molecular Formula – A chemical formula of a molecular compound.
8.2
Topics: The Nature of Covalent Bonding
Question: What is the result of electrons sharing in covalent bonds?
Answer: In covalent electron, sharing usually occurs so that atoms attain the
electron configuration of the noble gases.
Question: How do electron dot diagram structures represent shared electrons?
Chemistry Chapter 8 Review
Answer: Two dots represent a pair that is shared between two elements. A dash
represents a single pair, two dashes represent two pairs, and three dashes
represent three pairs.
Question: How do atoms form double or triple covalent bonds?
Answer: Atoms form double or triple covalent bonds if they can attain a noble gas
structure by sharing two pairs or three pairs of electrons.
Question: How are coordinate covalent bonds different from other covalent
bonds?
Answer: In a coordinate covalent bond, the shared electron pair comes from one
of the bonding atoms, not both.
Question: How is the strength of a covalent bond related to its bond dissociation
energy?
Answer: A large bond dissociation energy corresponds to a strong covalent bond.
Question: How are oxygen atoms bonded in ozone?
Answer: The actual bonding of oxygen atoms in ozone is a hybrid.
Question: What are some expectations to the octet rule?
Answer: Odd number of combined valence electrons, then it will violate the octet
rule
Vocabulary:
Single covalent bonds- When 2 electrons are shared between 2 atoms. 1 electron
is coming from each element.
Structural Formula- Shows the arrangement and represents the bonds with
dashes
Chemistry Chapter 8 Review
Unshared Pair - A pair of valence electrons that is not shared between 2 elements.
Double covalent bonds - When 4 electrons (2 pairs) that are shared between 2
atoms.
Triple covalent bonds- When 6 electron (3 pairs) that are shared between 2
atoms.
Coordinate covalent bonds- Is a bond where 1 atom is contributing the bonding
pair.
Polyatomic ion- A tightly bound group of atoms that have a group
Bond Dissociation Energy - The energy required to break the bond between two
covalently bonded atoms.
Resonance Structure – A structure that occurs when it is possible to draw two or
more valid electron dot structures that have the same number of electron pairs
for a molecule or ion.
8.3
Topics: Bonding Theories
Question: How are atomic and molecular orbitals related?
Answer: Atomic orbital belongs to just that atom and a Molecular orbital to the
entire molecule.
Question: How does VSEPR theory help predict the shapes of molecules?
Answer: The repulsion between electron pairs causes molecular shapes to adjust
so that the valence electron pairs stay as far apart as possible.
Question: In what ways is orbital hybridization useful in describing molecules?
Answer: It provides information about both molecular bonding and molecular
shape.
Chemistry Chapter 8 Review
Vocabulary:
Molecular Orbitals – Orbitals for a molecule.
Bonding Orbital – A molecular orbital that can be occupied by two electrons of a
covalent bond.
Sigma Bond – When two atomic orbitals combine to form a molecular orbital that
is symmetrical around the axis connecting two atomic nuclei. (Sigma bonds are
symmetrical. There is no overlapping of the nuclei.)
Pi Bond – When bonding electrons are most likely to be found in sausage-shaped
regions above and below the bond axis of the bonded atoms. (Pi Bonds are
sausage shaped and the nuclei overlaps and it’s not symmetrical)
Tetrahedral Angle – When the atom angles of a compound are 109.5 degrees,
called a tetrahedron.
VSEPR Theory – The repulsion between electron pairs causes molecular shapes to
adjust so that the valence-electron pairs stay as far away as possible.
Hybridization – When several atomic orbitals mix to form the same total number
of equivalent hybrid orbitals.
Shapes Page 233. Memorize ALL of them.
Chemistry Chapter 8 Review
8.4
Topics: Polar Bonds and Molecules
Question: How do electronegativity values determine the charge distribution in a
polar bond?
Answer: If it is more electronegative, it will attract more electrons, causing it to
have a partial charge.
Question: What happens in a polar bond?
Answer: In a polar bond one side of the molecule is positive and the other is
negative. Overall the entire molecule is neutral.
Question: How to intermolecular attractions compare with ionic and covalent
bonds?
Answer: Intermolecular attractions are weaker than either ionic or covalent
bonds.
Question: Why do network solids have high melting points?
Answer: The bonds are so strong that it takes a lot of energy to break the bonds.
Vocabulary:
Nonpolar Covalent Bond- Evenly shared.
Polar Covalent Bond- Not evenly shared.
Polar Bond- A covalent bond between atoms in which the electrons are shared
unequally.
Polar Molecule- One end of the molecule is slightly negative and the other end is
slightly positive
Chemistry Chapter 8 Review
Dipole- A molecule that has two poles
Dipole Interactions- Occur when polar molecules are attracted to one another.
Dispersion Forces- The weakest of all molecular interactions, are caused by the
motion of electrons.
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.