CHEM0010 - ALL CONTENT EXAM QUESTIONS AND
ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
LATEST UPDATE GRADED A++
Explain how a mass spectrometer works.
Sample is vaporised with heat.
Electron beam ionises sample.
Ion beam accelerated by electric field (so KE is constant).
Magnetic field deflects particles according to mass/charge ratio.
Lower m/z are deflected more; reach ion detector faster.
What is the Aufbau principle?
lowest energy orbitals are filled first.
Describe the properties of an electron.
Has wave-particle duality properties, so is described as a wavefunction.
Define wavefunction.
A mathematical description of the distribution of electrons in terms of position and time.
Explain the Heinsberg Uncertainty Principle in terms of electrons.
The electron's position and momentum (energy) cannot simultaneously be determined.
What is an orbital?
A defined region of space where an electron is most probably located.
,What method is used to determine the exact energy of electrons?
Spectroscopy.
What are the four quantum numbers and what do they represent?
Principal quantum number (n) - its shell (distance from nucleus).
Angular momentum quantum number (l) - subshell/shape of orbital
Magnetic quantum number (ml) - orientation of the orbital.
Spin quantum number (ms) - whether e spins clockwise or anticlockwise.
What values of n, l, ml and ms can there be?
n >= 1
0 =< l < n
-l =< m <= l
ms = -1/2 or 1/2
What is the radial distribution function?
The probability of an electron being found at the distance, r, from the nucleus.
What is the Pauli Exclusion Principle?
No two electrons in the same atom can have the same set of four quantum numbers.
What is the Pauli principle?
Only two electrons may occupy each orbital.
Explain why there is a small hump in the radial distribution function of a 2s
orbital. Why does this not happen to 2p electrons?
,2s electrons can penetrate the core 1s orbital and so spends time closer to the nucleus
and experiences stronger attraction, so energy is lowered.
2p electrons are more greatly shielded from the nuclear attraction, so have higher
energy.
What is Hund's rule?
If more than one orbital has the same energy, electrons will spread out to occupy the
maximum possible number of these which maximises the number of parallel spins.
(This reduces electrostatic repulsion and so provides a lower energy arrangement.)
What is spin correlation?
Electrons have lower energy when their spins are parallel because repulsion is reduced
and they stay further away from each other.
How many valance electrons does an element have?
# valence e = Group number
What is a covalent bond?
A shared pair of valance electrons between two atoms.
Explain what is meant by a resonance hybrid.
Some molecules may have multiple Lewis structures - each with a different resonance
form. The true structure is an average of these forms.
How many valence electrons in CO3^2-?
24
What is meant by hypervalency? Why does this arrise?
, Compounds which require more than an octet of electrons to draw a Lewis structure.
Due to the availability of low-lying d-orbitals to accommodate the extra electrons.
What are the names of the shapes of molecules with 2-7 bonding electron pairs?
linear, trigonal planar, tetrahedral, trigonal bipyramidal, octahedral,
pentagonal bipyramid.
What are the names of the shapes of molecules (based on tetrahedral shapes)
that contain 1 or two lone pairs?
Trigonal pyramidal
Bent
What are the names of the shapes of molecules (based on trigonal bipyramidal
shapes) that contain 1 or two lone pairs?
Disphenoidal, T-shaped
What are the names of the shapes of molecules (based on octahedral shapes)
that contain 1 or two lone pairs?
Square pyramidal
Square planar
Define degenerate.
Identical and undistinguishable in energy.
If a lone pair has a choice between an equatorial position and an axial position,
which will it occupy and why?
ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
LATEST UPDATE GRADED A++
Explain how a mass spectrometer works.
Sample is vaporised with heat.
Electron beam ionises sample.
Ion beam accelerated by electric field (so KE is constant).
Magnetic field deflects particles according to mass/charge ratio.
Lower m/z are deflected more; reach ion detector faster.
What is the Aufbau principle?
lowest energy orbitals are filled first.
Describe the properties of an electron.
Has wave-particle duality properties, so is described as a wavefunction.
Define wavefunction.
A mathematical description of the distribution of electrons in terms of position and time.
Explain the Heinsberg Uncertainty Principle in terms of electrons.
The electron's position and momentum (energy) cannot simultaneously be determined.
What is an orbital?
A defined region of space where an electron is most probably located.
,What method is used to determine the exact energy of electrons?
Spectroscopy.
What are the four quantum numbers and what do they represent?
Principal quantum number (n) - its shell (distance from nucleus).
Angular momentum quantum number (l) - subshell/shape of orbital
Magnetic quantum number (ml) - orientation of the orbital.
Spin quantum number (ms) - whether e spins clockwise or anticlockwise.
What values of n, l, ml and ms can there be?
n >= 1
0 =< l < n
-l =< m <= l
ms = -1/2 or 1/2
What is the radial distribution function?
The probability of an electron being found at the distance, r, from the nucleus.
What is the Pauli Exclusion Principle?
No two electrons in the same atom can have the same set of four quantum numbers.
What is the Pauli principle?
Only two electrons may occupy each orbital.
Explain why there is a small hump in the radial distribution function of a 2s
orbital. Why does this not happen to 2p electrons?
,2s electrons can penetrate the core 1s orbital and so spends time closer to the nucleus
and experiences stronger attraction, so energy is lowered.
2p electrons are more greatly shielded from the nuclear attraction, so have higher
energy.
What is Hund's rule?
If more than one orbital has the same energy, electrons will spread out to occupy the
maximum possible number of these which maximises the number of parallel spins.
(This reduces electrostatic repulsion and so provides a lower energy arrangement.)
What is spin correlation?
Electrons have lower energy when their spins are parallel because repulsion is reduced
and they stay further away from each other.
How many valance electrons does an element have?
# valence e = Group number
What is a covalent bond?
A shared pair of valance electrons between two atoms.
Explain what is meant by a resonance hybrid.
Some molecules may have multiple Lewis structures - each with a different resonance
form. The true structure is an average of these forms.
How many valence electrons in CO3^2-?
24
What is meant by hypervalency? Why does this arrise?
, Compounds which require more than an octet of electrons to draw a Lewis structure.
Due to the availability of low-lying d-orbitals to accommodate the extra electrons.
What are the names of the shapes of molecules with 2-7 bonding electron pairs?
linear, trigonal planar, tetrahedral, trigonal bipyramidal, octahedral,
pentagonal bipyramid.
What are the names of the shapes of molecules (based on tetrahedral shapes)
that contain 1 or two lone pairs?
Trigonal pyramidal
Bent
What are the names of the shapes of molecules (based on trigonal bipyramidal
shapes) that contain 1 or two lone pairs?
Disphenoidal, T-shaped
What are the names of the shapes of molecules (based on octahedral shapes)
that contain 1 or two lone pairs?
Square pyramidal
Square planar
Define degenerate.
Identical and undistinguishable in energy.
If a lone pair has a choice between an equatorial position and an axial position,
which will it occupy and why?
