CHEM 141 exam 3 2025 Questions and
Answers
What is the size of an atom based on? - --CORRECT ANSWER--The balance
between the attraction between the negatively charged electrons to the positively
charged protons in the nucleus, the repulsions between the electrons as they get
closer to each other.
Why the atoms size is decreasing across the periodic table - --CORRECT
ANSWER--As the number of protons increase, each electron in the valence shell is
attracted by an increasing number of protons in the nucleus. The more protons,
the larger the attractive force.
Effective nuclear charge - --CORRECT ANSWER--its a charge that the valence
electrons feel to the nucleus once we eliminated the core electrons.
Which is more electronegative?
F
Cl
Br
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,I - --CORRECT ANSWER--Fluorine because its valence electrons are closer to
the nucleus, smaller atoms are going to have a higher electronegativity.
Which is more electronegative?
C
N
O
Ne - --CORRECT ANSWER--Oxygen because it attracts bonding electrons more
tightly
Does C4H10 or C6H14 have a higher boiling point? and why? - --CORRECT
ANSWER--C6H14 has a higher boiling point because it is a larger molecule.
Larger molecules have a larger distortion of the electron cloud and therefore
stronger LDFs. When a substance boils, LDFs are overcome. Stronger LDFs mean
more energy (higher temp) is needed to overcome the interactions.
Use Valence Bond Theory to explain why rotation is possible around single bonds,
but not double bonds. - --CORRECT ANSWER--Single (sigma) bonds are formed
when atomic or hybrid orbitals overlap directly between the two nuclei (end-to-
end). When the bond rotates, the overlap stays the same so the bond is not broken.
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, Double bonds contain one sigma and one pi bond. Pi bonds are formed from the
side-to-side overlap and result in the overlap occurring above and below the plane
of the nuclei. If a pi bond were to rotate the overlap of the p-orbitals would be
broken and therefore the bond would break.
Electronegativity - --CORRECT ANSWER--An atom has a high effective nuclear
charge attracts its own valence electrons strongly and it attracts electrons from
other atoms in bonds.
CH4 hybridization and center geometry - --CORRECT ANSWER--sp3 and
tetrahedral
NH3 hybridization and center geometry - --CORRECT ANSWER--sp3 and
tetrahedral
H2O hybridization and center geometry - --CORRECT ANSWER--sp3 and
tetrahedral
C2H4 hybridization and center geometry - --CORRECT ANSWER--sp2 and
trigonal planar
CO2 hybridization and center geometry - --CORRECT ANSWER--sp and linear
Do molecules interact? - --CORRECT ANSWER--Yes, LDF's and their states of
matter (solid, liquid and gas)
Highest boiling point?
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Answers
What is the size of an atom based on? - --CORRECT ANSWER--The balance
between the attraction between the negatively charged electrons to the positively
charged protons in the nucleus, the repulsions between the electrons as they get
closer to each other.
Why the atoms size is decreasing across the periodic table - --CORRECT
ANSWER--As the number of protons increase, each electron in the valence shell is
attracted by an increasing number of protons in the nucleus. The more protons,
the larger the attractive force.
Effective nuclear charge - --CORRECT ANSWER--its a charge that the valence
electrons feel to the nucleus once we eliminated the core electrons.
Which is more electronegative?
F
Cl
Br
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 1
,I - --CORRECT ANSWER--Fluorine because its valence electrons are closer to
the nucleus, smaller atoms are going to have a higher electronegativity.
Which is more electronegative?
C
N
O
Ne - --CORRECT ANSWER--Oxygen because it attracts bonding electrons more
tightly
Does C4H10 or C6H14 have a higher boiling point? and why? - --CORRECT
ANSWER--C6H14 has a higher boiling point because it is a larger molecule.
Larger molecules have a larger distortion of the electron cloud and therefore
stronger LDFs. When a substance boils, LDFs are overcome. Stronger LDFs mean
more energy (higher temp) is needed to overcome the interactions.
Use Valence Bond Theory to explain why rotation is possible around single bonds,
but not double bonds. - --CORRECT ANSWER--Single (sigma) bonds are formed
when atomic or hybrid orbitals overlap directly between the two nuclei (end-to-
end). When the bond rotates, the overlap stays the same so the bond is not broken.
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 2
, Double bonds contain one sigma and one pi bond. Pi bonds are formed from the
side-to-side overlap and result in the overlap occurring above and below the plane
of the nuclei. If a pi bond were to rotate the overlap of the p-orbitals would be
broken and therefore the bond would break.
Electronegativity - --CORRECT ANSWER--An atom has a high effective nuclear
charge attracts its own valence electrons strongly and it attracts electrons from
other atoms in bonds.
CH4 hybridization and center geometry - --CORRECT ANSWER--sp3 and
tetrahedral
NH3 hybridization and center geometry - --CORRECT ANSWER--sp3 and
tetrahedral
H2O hybridization and center geometry - --CORRECT ANSWER--sp3 and
tetrahedral
C2H4 hybridization and center geometry - --CORRECT ANSWER--sp2 and
trigonal planar
CO2 hybridization and center geometry - --CORRECT ANSWER--sp and linear
Do molecules interact? - --CORRECT ANSWER--Yes, LDF's and their states of
matter (solid, liquid and gas)
Highest boiling point?
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