Quantum Theory Review Answer Key
1)
Draw a diagram of a wave and label the wavelength.
2)
Define:
A) wavelength - Distance between 2 similar points on adjacent waves
B) frequency - number of waves that pass a given point per second
C) Quantum – minimum amount of energy that can be gained or lost by an atom
D) Photon – a particle of light with one quantum of energy
3)
What determines the frequency of a light wave?
The amount of energy.
4)
How do we perceive the frequency of a light wave?
As a color
5)
When a light’s color changes from red to violet, what happens to its:
A) frequency increases
B) wavelength decreases
C) energy increases
6)
What units are used to measure:
A) frequency - Hertz (Hz) or 1/seconds
B) wavelength - meters (m)
C) energy – Joules (J)
7)
How do the waves drawn above compare in regards to:
A) wavelength - Wave A has a longer wavelength than B.
B) frequency - Wave A is a lower frequency than B.
C) energy – Wave A is lower in energy than B.
D) color – These are visible light waves then A is redder and B is more violet
8)
Describe the polarization.
Normal light waves vibrate in all directions about its direction of motion. If light passes
through, or reflects off of a material in which the particles are arranged in long lines, the
vibrations will be limited to only those that match the direction of the lines of particles. This
light will pass through a second filter with the same alignment, but will be blocked by a filter
aligned at a 90o angle to the direction of vibration.
9)
What is meant by wave interference?
When 2 waves pass through each other they interact by either adding together (constructive
interference) or subtracting from each other (negative interference) depending on how their
crests and troughs match up.
10)
Look at the two waves drawn below, what would be the result of these two waves
passing through each other as drawn?
Waves A and B will show
constructive interference and so will
add together to form a wave with a
higher amplitude
11)
Look at the two waves drawn below, what would be the result of these two waves
passing through each other as drawn?
Waves A and B will show destructive
interference and so will subtract from
each other to form a wave with a
smaller amplitude
12)
Describe diffraction.
Waves tend to bend when passing around an edge.
13)
How will the waves produced by diffraction of a wave through two slits interact?
If there are 2 slits present the new waves will interfere with each other forming a pattern of
light and dark areas. The light areas are places with positive interference. The dark areas are
places with negative interference.
14)
Describe the photoelectric effect.
When light shines on a piece of metal electrons are knocked free from the metal creating a
current.
15)
Describe the unexpected data that Max Planck got for black-body (hot object) emissions
of energy. What conclusion about energy did this result in?
Max Plank found that this light was not emitted continuously, but instead came off in discrete
packets.
16)
Which of the properties described in questions 8 through 15 are wave properties?
Polarization, interference and diffraction.
17)
Which of the properties described in questions 8 through 15 are particle properties?
Black-body emissions and photoelectric effect.
18)
What 2 measurements are related by Planck’s constant (h)?
Frequency and Energy.
19)
A light wave with a wavelength of 4.7 x 10 -9 m would:
A) move at c = 3.00 x 108m/s.
B) have a frequency of 6.4 x 1016Hz
𝐹=
𝑐
3.00 𝑥 108 𝑚/𝑠
=
= 6.4 𝑥 1016 𝐻𝑧
𝜆
4.7 𝑥 10−9 𝑚
C) have 4.2 x 10-17J energy.
20)
𝐸 = ℎ𝑓 = (6.626 𝑥 10−34 𝐽𝑠)(6.4 𝑥 1016 ⁄𝑠) = 4.2 𝑥 10−17 𝐽
What type of electromagnetic radiation is the light described in question #19?
Ultraviolet
21)
A light has 6.12 x 10 -23 J of energy, determine its:
A) wavelength
𝜆=
B) frequency
𝑓=
𝑐ℎ
𝐸
𝐸
ℎ
=
=
(3.00 𝑥 108 𝑚⁄𝑠)(6.626 𝑥 10−34 𝐽𝑠)
6.12 𝑥 10−23 𝐽
6.12 𝑥 10−23 𝐽
6.626 𝑥 10−34 𝐽𝑠
= 3.25 𝑥 10−3 𝑚 𝑜𝑟 0.00325 𝑚
= 9.24 𝑥 1010 𝐻𝑧
C) placement on the electromagnetic spectrum - microwaves
22)
Describe the placement of electrons in an atom at its:
A) ground state – all electrons will be in the lowest possible energy levels
B) excited state – some of the electrons in the atom will have moved up to higher
energy levels
23)
What causes an atom to move from its ground state to an excited state?
The atom absorbs energy causing an electron to move to a higher energy level.
24)
What happens when an atom returns from an excited state to its ground state?
Energy is given off as light of a specific frequency (color).
25)
Describe:
A) continuous spectrum – Colors blend from one to another (rainbow)
B) Emission (bright line) spectrum – Distinct lines of color, each representing a
specific energy.
26)
Which type of spectrum is unique (a fingerprint) for each element?
27)
Emission (bright line) spectrum
What instrument is used to view a bright line spectrum?
Spectroscope
28)
Describe the modern concept of the nature of light.
Light is both a particle and a wave (Duality).
29)
Describe the modern concept of the nature of an electron.
An electron is both a particle and a wave (Duality).
30)
31)
32)
Describe the shape, number of orbitals and electron capacity of the:
A)
s-Sublevel – spherical, 1 orbital, 2 electrons
B)
p-Sublevel – pear shaped, 3 orbitals, 6 electrons
Describe the number of orbitals and electron capacity of the:
A)
d-Sublevel – 5 orbitals, 10 electrons
B)
f-Sublevel – 7 orbitals, 14 electrons
Describe Heisenberg’s Uncertainty Principle.
We can never be certain of both the momentum and position of an electron. The better we
measure on of these values the less certain we are of the other. The best we are able to do is say
where the electron most likely is based on probability.
33)
What did Louis de Broglie theorize?
Electrons have both a wave and particle nature. An electron can only orbit the nucleus at a
distance where its wave can exist.
34)
What was Schrodinger’s contribution?
Schrodinger developed a set of equations that predicts the shape of the orbitals.
35)
How do we use waves to explain the placement of the Principle Energy Levels?
An electron can only orbit the nucleus at a distance where its wave can exist.
36)
What are the maximum numbers of electrons in each of the following energy levels?
A) n = 1 - 2
B) n = 2 - 8
C) n = 3 - 18
D) n = 4 - 32
37)
How did Bohr explain the existence of hydrogen’s bright line spectrum?
When an excited atom returns to the ground state the electron gives off energy. The distance
the electron jumped between energy levels determines the energy of the light given off. Since
energy is associated with frequency and we perceive frequency as color. Each jump results in
a distinct line on the spectrum.
38)
Describe the following rules.
A) Aufbau Principle - An electron will occupy the lowest energy orbital available to it
B) Pauli’s Exclusion Principle – Two electrons in an atom cannot be described by the
same set of 4 quantum numbers. For 2 electrons to occupy the same orbital they must
spin in opposite directions
C) Hund’s Rule – Orbitals of equal energy are occupied by 1 electron each before any orbital is
occupied by a second electron. All unpaired electrons must spin in the same direction.
39)
For an atom of the element Iridium use the rules and the electron configuration
diagram to write an:
A) electron configuration
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d7
B) orbital notation
C) noble gas notation
[Xe] 6s2 4f14 5d7
40)
Draw a Bohr-Rutherford Model of the Iridium atom described in question #38.
41)
What rule(s) are being violated in the following orbital notation for a vanadium atom.
Give an explanation for why you feel the rule(s) have been violated for each of the
rules you named.
Hund’s Rule – electrons are paired in the 3d orbital before there is one electron in each
available orbital
41)
The diagram below illustrates an oxygen atom. It appears to violate one of the rules,
but is accurately portraying this particular atom. What is special about this atom?
This an excited atom in which electrons have moved to a higher energy level due to
their absorbing energy.
42)
The diagram below illustrates an atom of Neon, what is special about this atom?
It has 8 electrons in its outer most energy level.
43)
How many Quantum numbers are needed to describe the energy state of an electron?
What property is each number describing?
Four quantum numbers are required. They describe the Energy level, shape of the
orbital, 3 dimensional orientation of the orbital and spin of each electron.