1
CEM 141 Chapter 3 Test Questions with
Answers (100% Correct Answers)
Similarities between LDF and Covalent Bond Answer: they have similar
causes: electrostatic attraction of the electron of one atom to the nucleus of the
other
Differences between LDF and Covalent Bond Answer: 1. magnitude of
attraction
2. how the electrons are arranged in the new species formed by the interaction
Why do bonds form between atoms? Answer: because valence electrons are
attracted to the nuclei of other atoms
Covalent Bonds Answer: 1. valence electrons from one atom become attracted
to the nucleus of the other atom
2. each nucleus is attracting both electrons
3. when bonds form energy is released to surrounding
What is bond length? Answer: the most stable distance between atoms (lowest
PE)
Molecular Orbital Theory Answer: 1. atomic orbitals can combine
constructively to form a molecular orbital of lower energy (in phase)
2. atomic orbitals can combine destructively to form a molecular orbital of
higher energy (out of phase)
3. combine n atomic orbitals--> n molecular orbitals
4. Bonding and Anti-bonding orbitals
a. both are in the same place of space, just at different energies
,2
Bonding Orbitals Answer: 1. of lower energy than the atomic orbitals
(typically)--> stabilizing
a. electrons in bonding orbitals make the species more stable
Anti-bonding Orbitals Answer: 1. of higher energy than the atomic orbitals and
destabilizing
a. electrons in anti-bonding orbitals make the species less stable
Why do 2 H atoms form a bond while 2 He atoms don't? Answer: 1. In H2: 2
electrons in a bonding orbital make 1 bond (H2 has one bond between 2 H
atoms)
2. In He: 2 electrons in a bonding MO is stabilizing, but 2 electrons in an anti-
bonding MO cancel out stabilization (so no bonds between He atoms)
Bonding in H and He Answer: 1. In hydrogen-hydrogen, only the bonding MO
is occupied, leading to a net stabilization of the interaction
a. to break the bond, enough energy has to be added to raise an electron to the
anti-bonding orbital
2. In helium-helium, both bonding and anti-bonding molecular orbitals are
occupied. Because their energies (negative for bonding orbital and positive for
anti-bonding orbital) are equal and opposite, there is no net stabilization for
interaction
If we combine 2 atoms with 10 atomic orbitals each, how many molecular
orbitals will result? Answer: 20
If 2 elements in the second row (ex. 2 O atoms) were to interact, how many
molecular orbitals would be generated by the atomic orbitals in the core and
valence shells? Answer: 1. O: 1s2 2s2 2p6
a. there are 5 atomic orbitals from each O being combined, 5+5= 10
i. Answer: 10
, 3
How many bonds form between 2 O atoms? Answer: 2 bonds (only concerned
with valence electrons)
What properties do metals have? Answer: 1. shiny
2. conduct electricity and heat
a. because electrons can move freely
3. malleable and ductile
a. malleable because atoms can move with respect to one another
4. may be colored (gold, copper)- silver is colorless (like most metals)
How does bonding in metals explain their properties? Answer: 1. lots of atomic
orbitals combine with each other to form molecular orbitals (an equal number)
2. As the number of Molecular Orbital's increases, the energy distance between
them decreases and they form bands of Molecular Orbitals (of almost
continuous energy)
3. electrons can move freely between Molecular Orbitals and over whole
system
Why are metals shiny? (properties of metals) Answer: 1. Absorption of a
photon will promote an electron to a higher energy level
2. It immediately falls back down-emitting a photon-the metal shines
3. the metal interacts with light of many wavelengths, so the metal appears
white or colorless (silvery)
a. metals are shiny because photons of many wavelengths are absorbed and
then emitted
How is metallic bonding, which causes the metal to shine, different from the
photoelectric effect? Answer: 1. In Metallic bonding, the electron is promoted
CEM 141 Chapter 3 Test Questions with
Answers (100% Correct Answers)
Similarities between LDF and Covalent Bond Answer: they have similar
causes: electrostatic attraction of the electron of one atom to the nucleus of the
other
Differences between LDF and Covalent Bond Answer: 1. magnitude of
attraction
2. how the electrons are arranged in the new species formed by the interaction
Why do bonds form between atoms? Answer: because valence electrons are
attracted to the nuclei of other atoms
Covalent Bonds Answer: 1. valence electrons from one atom become attracted
to the nucleus of the other atom
2. each nucleus is attracting both electrons
3. when bonds form energy is released to surrounding
What is bond length? Answer: the most stable distance between atoms (lowest
PE)
Molecular Orbital Theory Answer: 1. atomic orbitals can combine
constructively to form a molecular orbital of lower energy (in phase)
2. atomic orbitals can combine destructively to form a molecular orbital of
higher energy (out of phase)
3. combine n atomic orbitals--> n molecular orbitals
4. Bonding and Anti-bonding orbitals
a. both are in the same place of space, just at different energies
,2
Bonding Orbitals Answer: 1. of lower energy than the atomic orbitals
(typically)--> stabilizing
a. electrons in bonding orbitals make the species more stable
Anti-bonding Orbitals Answer: 1. of higher energy than the atomic orbitals and
destabilizing
a. electrons in anti-bonding orbitals make the species less stable
Why do 2 H atoms form a bond while 2 He atoms don't? Answer: 1. In H2: 2
electrons in a bonding orbital make 1 bond (H2 has one bond between 2 H
atoms)
2. In He: 2 electrons in a bonding MO is stabilizing, but 2 electrons in an anti-
bonding MO cancel out stabilization (so no bonds between He atoms)
Bonding in H and He Answer: 1. In hydrogen-hydrogen, only the bonding MO
is occupied, leading to a net stabilization of the interaction
a. to break the bond, enough energy has to be added to raise an electron to the
anti-bonding orbital
2. In helium-helium, both bonding and anti-bonding molecular orbitals are
occupied. Because their energies (negative for bonding orbital and positive for
anti-bonding orbital) are equal and opposite, there is no net stabilization for
interaction
If we combine 2 atoms with 10 atomic orbitals each, how many molecular
orbitals will result? Answer: 20
If 2 elements in the second row (ex. 2 O atoms) were to interact, how many
molecular orbitals would be generated by the atomic orbitals in the core and
valence shells? Answer: 1. O: 1s2 2s2 2p6
a. there are 5 atomic orbitals from each O being combined, 5+5= 10
i. Answer: 10
, 3
How many bonds form between 2 O atoms? Answer: 2 bonds (only concerned
with valence electrons)
What properties do metals have? Answer: 1. shiny
2. conduct electricity and heat
a. because electrons can move freely
3. malleable and ductile
a. malleable because atoms can move with respect to one another
4. may be colored (gold, copper)- silver is colorless (like most metals)
How does bonding in metals explain their properties? Answer: 1. lots of atomic
orbitals combine with each other to form molecular orbitals (an equal number)
2. As the number of Molecular Orbital's increases, the energy distance between
them decreases and they form bands of Molecular Orbitals (of almost
continuous energy)
3. electrons can move freely between Molecular Orbitals and over whole
system
Why are metals shiny? (properties of metals) Answer: 1. Absorption of a
photon will promote an electron to a higher energy level
2. It immediately falls back down-emitting a photon-the metal shines
3. the metal interacts with light of many wavelengths, so the metal appears
white or colorless (silvery)
a. metals are shiny because photons of many wavelengths are absorbed and
then emitted
How is metallic bonding, which causes the metal to shine, different from the
photoelectric effect? Answer: 1. In Metallic bonding, the electron is promoted
