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Michigan State University
CEM 141 CEM 141 MSU Exam 2 Questions
and Answers 2026 Latest Update
Which reaction requires the most energy?
A. N(g) → N+(g) + e -
B. N+(g) → N2+(g) + e -
C. F(g) → F+(g) + e -
D. F+(g) → F2+(g) + e - Ans: D. F+(g) → F2+(g) + e -
Fluorine has a higher effective nuclear charge than Nitrogen - so it is harder
to remove an electron (takes more energy because the electron is more
strongly attracted by the nucleus). Effective nuclear charge is the same for F
and F+ because the number of protons and core electrons are not changed.
However, when the number of electrons is reduced, the repulsion between
electrons decreases which results in a decrease in the radius of the electron
cloud because the point at which attractions and repulsions are balanced is
closer to the nucleus when there is less repulsion. When the radius of the
electron cloud decreases, the strength of the attraction between the nucleus
and the valence electrons increases which increases the amount of energy
required to remove an electron (ionization energy).
Which has a larger atomic radius? Mg or Ar and why. Ans: Mg, because its
valence electrons are not as strongly attracted towards the nucleus as those
in Ar.
The effective nuclear charge on Mg is smaller - on Ar the electrons are more
strongly attracted and therefore the electron cloud shrinks in towards the
nucleus until the e-e repulsions come into effect.
© 2026 All rights reserved
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Consider the isoelectronic (they all have the same number of electrons)
species Na+, Mg2+, Ne, and F-, which of these has the smallest radius? Ans:
Mg2+
All the species have the same number of electrons - but different number of
protons. Mg2+ has the highest proton to electron ratio and therefore the
highest effective nuclear charge and the strongest attraction between the
protons and electrons - which pulls the electron cloud towards the nucleus
until the repulsions take effect.
When and where were the carbon and oxygen atoms in your body created?
Ans: Within stars and stellar explosions
Iodine exists as molecules of I2 and silicon dioxide exists as an extended
network of Silicon-oxygen bonds (similar to diamond). They both are solids
at room temperature, but which do you think has the higher melting point
and why? Ans: Silicon dioxide because to melt it you would have to break
covalent bonds.
Does one molecule of water have a boiling point? Ans: No
Why does one molecule of water not have a boiling point? Ans: The boiling
point is the temperature at which the particles change from liquid to gas. If
there is only one particle the words liquid and gas (and solid for that
matter) are meaningless.
Why do covalent bonds form? Ans: - Because electrons from one atom are
attracted to the nucleus of another atom.
- Because the formation of a bond results in a stable system that would
require the input of energy to change.
Which of the following are correct statements?
I. Covalent bonds are interactions within molecules.
II. Covalent bonds are interactions between separate molecules.
III. LDFs are typically interactions between separate molecules, but can
occur within a single large molecule.
IV. LDFs are within molecules. Ans: I. Covalent bonds are interactions within
molecules.
© 2026 All rights reserved
Michigan State University
CEM 141 CEM 141 MSU Exam 2 Questions
and Answers 2026 Latest Update
Which reaction requires the most energy?
A. N(g) → N+(g) + e -
B. N+(g) → N2+(g) + e -
C. F(g) → F+(g) + e -
D. F+(g) → F2+(g) + e - Ans: D. F+(g) → F2+(g) + e -
Fluorine has a higher effective nuclear charge than Nitrogen - so it is harder
to remove an electron (takes more energy because the electron is more
strongly attracted by the nucleus). Effective nuclear charge is the same for F
and F+ because the number of protons and core electrons are not changed.
However, when the number of electrons is reduced, the repulsion between
electrons decreases which results in a decrease in the radius of the electron
cloud because the point at which attractions and repulsions are balanced is
closer to the nucleus when there is less repulsion. When the radius of the
electron cloud decreases, the strength of the attraction between the nucleus
and the valence electrons increases which increases the amount of energy
required to remove an electron (ionization energy).
Which has a larger atomic radius? Mg or Ar and why. Ans: Mg, because its
valence electrons are not as strongly attracted towards the nucleus as those
in Ar.
The effective nuclear charge on Mg is smaller - on Ar the electrons are more
strongly attracted and therefore the electron cloud shrinks in towards the
nucleus until the e-e repulsions come into effect.
© 2026 All rights reserved
, 2 | Page
Consider the isoelectronic (they all have the same number of electrons)
species Na+, Mg2+, Ne, and F-, which of these has the smallest radius? Ans:
Mg2+
All the species have the same number of electrons - but different number of
protons. Mg2+ has the highest proton to electron ratio and therefore the
highest effective nuclear charge and the strongest attraction between the
protons and electrons - which pulls the electron cloud towards the nucleus
until the repulsions take effect.
When and where were the carbon and oxygen atoms in your body created?
Ans: Within stars and stellar explosions
Iodine exists as molecules of I2 and silicon dioxide exists as an extended
network of Silicon-oxygen bonds (similar to diamond). They both are solids
at room temperature, but which do you think has the higher melting point
and why? Ans: Silicon dioxide because to melt it you would have to break
covalent bonds.
Does one molecule of water have a boiling point? Ans: No
Why does one molecule of water not have a boiling point? Ans: The boiling
point is the temperature at which the particles change from liquid to gas. If
there is only one particle the words liquid and gas (and solid for that
matter) are meaningless.
Why do covalent bonds form? Ans: - Because electrons from one atom are
attracted to the nucleus of another atom.
- Because the formation of a bond results in a stable system that would
require the input of energy to change.
Which of the following are correct statements?
I. Covalent bonds are interactions within molecules.
II. Covalent bonds are interactions between separate molecules.
III. LDFs are typically interactions between separate molecules, but can
occur within a single large molecule.
IV. LDFs are within molecules. Ans: I. Covalent bonds are interactions within
molecules.
© 2026 All rights reserved
