Atomic and Nuclear Physics - 1 - Nuclear Reaction
 The nucleus is composed of two nucleons,
______________ (no) and _______________ (p1)
 The number of protons is known as the
_______________ _____________ or (Z)
 The total number of protons and neutrons is the
_________________ ___________ or (A)
 An element can have more than one mass
number, these are called _______________
They have the same number of ___________ but
different numbers of ______________.
 Most everyday isotopes are stable.
 Some isotopes are __________ and decay
spontaneously while emitting...
 These unstable isotopes are called
_________________ or _________________
A radionuclide with too many nucleons can get rid of 2
protons and 2 neutrons by emitting an alpha particle.
Nuclear Notation
There are three types of nuclear radiation:
Alpha particles:
Beta particles:
Gamma Radiation:
A radionuclide with too many neutrons can reduce that
number by one by emitting a negative beta particle:
This is shown by the equation:
Note that the number of ________________ and
_________________ are always conserved.
A radionuclide with too many protons can reduce that
number by one by emitting a positive beta particle:
During this process a ___________ is converted to a
______________. Therefore the atomic number is ...
The energy and momentum are not conserved in our
beta decay equations without including the neutrino.
A neutrino has no __________, no ____________ and
travels at...
During this process a ___________ is converted to a
______________. Therefore the atomic number is ...
β+
β-
If a nucleus becomes excited it sheds energy by emitting
gamma radiation.
The _________________ _____________ and
______________ of the nucleus does not change as a
result of gamma radiation.
The fraction of a radionuclide remaining after a certain
time period is an exponential function of the decay
constant and time.
Where:
The half-life of a radionuclide is defined as the time it
takes for...
2 – Mass-Energy Equivalence
Einstein proposed that an objects’ mass increases with
its speed. Since performing work on an object increases
its speed, then mass must also be a form of energy.
Example: An elementary particle called a pion with a mass of
2.40x10-28kg decays into electromagnetic radiation. How much
energy is released by the decay of a pion at rest?
This is expressed by the equation:
He also suggested that ___________ can be converted
to ___________ and vice versa.
A change in energy is therefore:
A helium atom is made of 2 protons, 2 neutrons and 2
electrons. However, when you add up the total mass of the
nucleons it is _________ than the mass of a helium atom.
This means that when the nucleons came together to form the
nucleus, some of the mass...
This “mass defect” explains the _____________ of the nucleus.
This energy is known as _________________ _____________.
 It is important to realize that the binding energy is not something that holds
the nucleus together, rather it is the energy necessary to _____________
____ a nucleus.
 What holds the nucleus together is the __________ ______________ force.
 Unlike electrostatic or gravitational forces, the strong nuclear force acts
over _____________ _________________.
 Strong nuclear force is also much ________________ than electrostatic or
gravitational forces.
 For this reason, protons which _________ each other are held tightly
together in the nucleus.
When a uranium nucleus fissions, it releases some ________ __________.
These excess neutrons can initiate fission in nearby uranium nuclei,
thereby causing a ____________ ___________________.
The minimum mass of material required to sustain a chain reaction is
called the _______________ ___________.
Nuclear fission occurs when a nucleus
____________ in to two roughly equal
sized smaller nuclei as well as some
______ ___ ________________.
Since the binding energy of the parent
nucleus is less than the daughter nuclei,
______________ is released.
3 – Photons and the Photoelectric Effect
Summarize J.J. Thompson’s cathode ray experiment and
findings:
Summarize Robert Millikan’s oil drop experiment and findings:
 Einstein proposed the idea that light travels as
_____________ particles or _________________
rather than as waves.
 These can only be ______________ or
____________ in whole units.
 Each light “particle” or ________________ has an
energy corresponding to its frequency and Planck’s
Constant.
Max Planck explained blackbody radiation with his theory that
thermal oscillators have ___________ quantities of energy.
Planck’s Quantum Hypothesis
Where: n =
f=
h=
Therefore the smallest packet of energy is called a
________________ of __________________
Example: Estimate the number of photons emitted per
second from a 60 W light bulb assuming that 10% of the
electrical energy is converted to light.
What is the light energy emitted by the bulb per second?
The Photoelectric Effect: When light strikes the surface of...
Classical Theory could not explain several of characteristics
of the Photoelectric Effect
Assume that the average wavelength of light is 550 nm.
How many photons are emitted by the light bulb per
second?
1. Kinetic energy of photoelectrons is...
2. No photoemissions for light...
3. Photocurrent flows immediately when...
Einstein explained the photoelectric effect using quantum theory.
The maximum kinetic energy of photoelectron is
 A photon of light has a...
 The electron is bound to the metal by ___________ ____________
Where: hf =
 As a result some of the photon’s energy does...
φ=
 The remaining energy goes into...
Example: Determine the maximum speed of a
photoelectron from a metal of known threshold
frequency.
The Compton Effect
Compton observed the scattering of x-rays by various materials.
He discovered that scattered radiation always had...
Assuming: me = 9.1x10-31 kg, ho = 4.7x1014 Hz,
λ = 900 nm
What is the photon energy?
He also determined that the change in wavelength depends on the
________________ ____________ but not the __________________
__________________.
What is the work function?
Compton assumed that the photons acted as _____________ colliding
elastically with _______________.
What is the maximum kinetic energy of the
photoelectron?
A photons momentum is given by relativistic theory:
What is the maximum speed of the
photoelectron?
The change in wavelength is given by:
This can be combined with the expression for energy of a photon from
quantum theory, the momentum of a photon is related to wavelength.
4 – Atomic Energy Levels
Summarize Blamer’s findings:
Summarize Rutherford’s gold foil experiment and its
findings:
Bohr proposed the quantum model of the hydrogen atom:
 Bohr assumed that the electron orbited the proton in the nucleus in a _________ ________
 Next he assumed that the angular momentum was ___________
and could only have discreet values
 The integer “n” is known as the _______________ ____________ _____________
 It follows that the electron’s orbit can only have certain possible ___________.
 For atoms with a single electron the energy levels are:
En = Z2 E1
n2
(General Formula)
En = -13.6 eV (Hydrogen only)
n2
 The allowed orbits in the Bohr Model are referred to as ____________ _________.
 The lowest energy level is called the __________ ___________.
 Higher energy levels are called ______________ _____________.
 An electron must be given...
 The energy necessary to completely free the electron from the atom is called
_________________ _________________.
 When an electron transitions from a excited state to the ground state, energy is
emitted as a _____________.
 The energy of this photon is equal to the ___________ _____________ between
the two levels.
 Therefore only a photon with a particular _______________ or ______________
can be emitted during a particular transition.
Example:
Determine the wavelength of light that is emitted when an electron transitions from the n = 5 to n = 2 energy levels.
What is the energy of the emitted photon?
What is the photon wavelength associated with this energy?
5 – Wave-Particle Duality
de Broglie reasoned that if light can behave as both a wave
and a particle then maybe a material particle can also
behave as a wave.
Example: what is the de Broglie wavelength of a 5.0 kg
bowling ball that is traveling at 2.0 m/s?
He proposed that the wavelength of a matter wave is related
to its momentum:
Where:
de Broglie used his hypothesis to explain Bohr’s atomic
energy theory of hydrogen.
This is similar to a photon of light:
Electrons travel in discreet circular orbits, and so the
matter wave is a ____________ ____________ wave.
The standing wave can only have an __________ ______
of wavelengths.
This wavelength is known as the de Broglie wavelength
The radius of a Bohr orbit is related to an
integral number of de Broglie wavelengths.
 The wavelengths of ordinary objects are...
 This is not the case for tiny and (relatively) slow moving objects such as
________________
 Davisson and Germer were able to show that electrons will __________
when striking a crystal of nickel just like light.
 Thomson was also able to show that electrons can scatter just like
_____________.
 An important application of electron diffraction is the scanning electron
microscope which has a much greater resolution than light microscopes
because...