CEM 141 MSU Exam 2 QUESTIONS &
ANSWERS(RATED A+)
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 - - ANSWERD. 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. - ANSWERMg, 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.
Consider the isoelectronic (they all have the same number of electrons) species Na+,
Mg2+, Ne, and F-, which of these has the smallest radius? - ANSWERMg2+
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? -
ANSWERWithin 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? - ANSWERSilicon dioxide
because to melt it you would have to break covalent bonds.
, Does one molecule of water have a boiling point? - ANSWERNo
Why does one molecule of water not have a boiling point? - ANSWERThe 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? - ANSWER- 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. - ANSWERI. Covalent bonds are interactions within
molecules.
and
III. LDFs are typically interactions between separate molecules, but can occur within a
single large molecule.
Why are metals shiny? - ANSWERBecause they absorb photons and re-emit them.
Metals have molecular orbitals that are very close together in energy. They can absorb
almost any wavelength of light because the gap between the levels is negligible. The
absorbed light can then be re-emitted.
Wavelength (h) - ANSWER- the distance from peak to peak
- measured in (m)
Frequency (v) - ANSWER- number of wavefronts per second
- measured in (Hz=s^-1)
If a reaction occurs between a compound that has a lemon smell and one that has a
rose smell what will the product smell like?
Lemon Smell+Rose Smell ---> Smell? - ANSWERIt is impossible to predict the smell of
the product.
Give the reasoning for your answer.
The properties of new substances depend on its molecular structure - the properties are
emergent.
ANSWERS(RATED A+)
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 - - ANSWERD. 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. - ANSWERMg, 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.
Consider the isoelectronic (they all have the same number of electrons) species Na+,
Mg2+, Ne, and F-, which of these has the smallest radius? - ANSWERMg2+
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? -
ANSWERWithin 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? - ANSWERSilicon dioxide
because to melt it you would have to break covalent bonds.
, Does one molecule of water have a boiling point? - ANSWERNo
Why does one molecule of water not have a boiling point? - ANSWERThe 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? - ANSWER- 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. - ANSWERI. Covalent bonds are interactions within
molecules.
and
III. LDFs are typically interactions between separate molecules, but can occur within a
single large molecule.
Why are metals shiny? - ANSWERBecause they absorb photons and re-emit them.
Metals have molecular orbitals that are very close together in energy. They can absorb
almost any wavelength of light because the gap between the levels is negligible. The
absorbed light can then be re-emitted.
Wavelength (h) - ANSWER- the distance from peak to peak
- measured in (m)
Frequency (v) - ANSWER- number of wavefronts per second
- measured in (Hz=s^-1)
If a reaction occurs between a compound that has a lemon smell and one that has a
rose smell what will the product smell like?
Lemon Smell+Rose Smell ---> Smell? - ANSWERIt is impossible to predict the smell of
the product.
Give the reasoning for your answer.
The properties of new substances depend on its molecular structure - the properties are
emergent.
