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Michigan State University
CEM 141 CEM 141 exam 3 Questions and
Answers 2026 Latest Update
Predict, draw models (pictures), and explain why relative melting points and
boiling points for substances that exist as molecules (like H2) differ from
those that exist as continuous extended networks (like diamond or metals).
Ans: discrete atoms: lower melting/boiling points, are not diatomic
small molecules: lower melting/boiling points, diatomic, lower because are
only held together by LDFs, which are substantially weaker than continuous
extended networks
continuous extended networks: higher melting/boiling points, higher
because covalent bonds have to be broken in order to turn solids to liquids,
liquids to gas
Compare and contrast the molecular orbital bond model and the valence
bond model. What are the similarities/differences? Ans: molecular orbital
bond model: atomic orbitals combine to form an equal number of molecular
orbitals, each orbital can contain up to 2 electrons, electrons in bonding
orbitals stabilize the system, electrons in antibonding orbitals make it less
stable, electrons are delocalized
valance bond model: atomic orbitals overlap to form a bond, the greater the
overlap, the stronger the bond, each bond is made up of 2 electrons,
electrons are localized in the bond
Describe the bonding in diamond and graphite in terms of the hybrid orbital
model (valence bond theory). Explain how the macroscopic properties of
diamond and graphite (appearance, melting point, strength, electricity
conductance, etc.) can be explained in therms of the kind of bonding that
occurs in these networks. Ans: orbitals are hybridized into 4 hybrid orbitals
all with the same energy and atoms are covalently bonded to each other in a
covalent network.
© 2026 All rights reserved
Michigan State University
CEM 141 CEM 141 exam 3 Questions and
Answers 2026 Latest Update
Predict, draw models (pictures), and explain why relative melting points and
boiling points for substances that exist as molecules (like H2) differ from
those that exist as continuous extended networks (like diamond or metals).
Ans: discrete atoms: lower melting/boiling points, are not diatomic
small molecules: lower melting/boiling points, diatomic, lower because are
only held together by LDFs, which are substantially weaker than continuous
extended networks
continuous extended networks: higher melting/boiling points, higher
because covalent bonds have to be broken in order to turn solids to liquids,
liquids to gas
Compare and contrast the molecular orbital bond model and the valence
bond model. What are the similarities/differences? Ans: molecular orbital
bond model: atomic orbitals combine to form an equal number of molecular
orbitals, each orbital can contain up to 2 electrons, electrons in bonding
orbitals stabilize the system, electrons in antibonding orbitals make it less
stable, electrons are delocalized
valance bond model: atomic orbitals overlap to form a bond, the greater the
overlap, the stronger the bond, each bond is made up of 2 electrons,
electrons are localized in the bond
Describe the bonding in diamond and graphite in terms of the hybrid orbital
model (valence bond theory). Explain how the macroscopic properties of
diamond and graphite (appearance, melting point, strength, electricity
conductance, etc.) can be explained in therms of the kind of bonding that
occurs in these networks. Ans: orbitals are hybridized into 4 hybrid orbitals
all with the same energy and atoms are covalently bonded to each other in a
covalent network.
© 2026 All rights reserved
