Physics 30
Atomic Physics
Name : ___________________
Physics 30
Atomic Physics – Model of the Atom
(Dalton/Thomson/Rutherford)
Name: ____________________
Date: _____________________
Dalton
Dalton was the first scientist who proposed a model for the atom. He suggested that an
atom was a tiny, indivisible and indestructible chunk of matter (ie. the billiard ball
model). This led to the development of a system of relative masses (H=1, O=16),
Periodic Table. The problem with the model was discovered when experiments found
that the atom was divisible, having more elementary particles in the second half of the 19th century.
Cathode Rays
However, with the development of cathode ray tubes and
the discovery of cathode rays, the model of the atom
needed to be revised. A cathode ray tube consists of a
set of parallel plates (electrodes) placed inside a glass
tube that contains a gas under low pressure. When
voltage is applied across the parallel plates/electrodes,
the gas in the tube will glow and a cathode ray will be
emitted from one of the electrodes (ie. cathode).
J. J. Thomson
J.J. Thomson did a lot of his work with cathode ray tubes and observed
some interesting properties of the cathode rays.
• Travelled in straight lines
• Could be deflected by both magnetic and electrical fields
(therefore, cathode rays could not be EMR)
• It didn’t matter what the cathode ray tube was made out of (ie. type
of gas used or the type of metal used for the electrodes), the
properties of the emitted cathode rays remained the same.
Thomson applied an external electric field (using a second
set of parallel plates) and noticed that the rays would always bend
towards the positively charged plate. He discovered that the
cathode rays were actually tiny, negatively charged particles – the
electron! With the discovery of the electron, Thomson revised the
model of the atom to what was referred to as the “raisin-bun” or
“plum-pudding” model. Small, negatively charged particles
(electrons) where embedded in a positively charged sphere. The
atom now had components, instead of being an indivisible chunk.
Thomson continued to work with the cathode ray tubes to try and determine the charge-to-mass ratio of
an electron. By applying an external magnetic field to the cathode rays travelling in a straight line,
Thomson noticed the cathode rays bent in a circular path and he measured the radius of curvature.
He could calculate the charge to mass ratio using deflection by a magnetic field. Using electric plates to
create electric fields to balance, he found speed.
𝐹𝑚 = 𝐹𝑐
Mass Spectrometer: Figure 15.8, Pg.759
Rutherford’s Scattering Experiment
Rutherford shot alpha particles
were directed toward a very thin gold
foil. He observed that although most of
the alpha particles passed through the
gold foil, a few were scattered at various
angles (some were even scattered back
along their original path). This was like
shooting bullets at a piece of tissue paper
and finding some of them bounced back
from the paper. Based of his
observations, Rutherford concluded the mass of an atom is not evenly distributed throughout the atom
as proposed by Thomson and his raisin bun model, but instead the bulk of the mass (the positive part of
the atom) is concentrated in a very small region of the atom (i.e. called the nucleus). The bulk of the
volume of an atom consists of the electrons (small and not much mass).
This explained why most of the alpha particles passed through undeflected because the electrons
would not be able to deflect the larger alpha particles. However, the more massive, but small volume
center, would cause only some alpha particles to be deflected by collision or electrostatic repulsion.
But there was a flaw to Rutherford’s model. If the positive nucleus is concentrated in the center of
the atom, what keeps the electrons from being pulled into the nucleus due to electrostatic attraction
and resulting in the atom collapsing?
The planetary/nuclear model of the atom was then proposed
and explained that if the electrons were orbiting the nucleus (like
planets orbit the sun) the electrons would stay in a circular orbit.
But an accelerating charged particle will emit EMR and if the
electron is emitting energy, it will lose kinetic energy and spiral
into the nucleus.
Examples 1
Charged particles are traveling horizontally at 3.60x10⁶ m/s when they enter a vertical magnetic field of
0.710 T. If the radius of the arc of the deflected particles is 9.50x10 -2 m, what is the charge to mass
ratio of the particles?
Examples 2
What is the speed of an electron that passes through an electrical field of 6.30x103 N/C and a magnetic
field of 7.11x10-3 T undeflected? Assume the magnetic field and electrical field are perpendicular to
each other.
Homework Pg. 756 #1-3, Pg. 758 #1-3
Physics 30
Atomic Physics – Milikan’s Oil Drop
Name: ____________________
Date: _____________________
Millikan performed an experiment from which he was able to determine the elementary charge of an
electron. Recall, a negative charge is due to an excess of electrons and a positive charge is due to a
shortage of electrons.
In his experiment, he blew oil drops
between horizontal parallel plates.
When no voltage was applied between
the parallel plates, the oil drops would
fall to the bottom plate due to the
force of gravity (Fg). Force of gravity
is now considerable because an oil drop
is not an atomic particle, and the mass
of the oil drop is significant.
When a voltage was supplied to the
plated, some of the oil particles would
rise to the top, some would remain
suspended, and some particles would
fall faster or slower to the bottom. All
these situations can be explaining by
the gravitational and electrical forces
acting on the oil drop.
Note, when solving Millikan type problems:
•
•
Always start with a free body diagram and a Fnet equation.
When the oil drop is suspended or moving at a constant speed (i.e. no acceleration), the
gravitational force and the electrical force acting on the oil drop are equal (i.e. Fnet = 0.0N)
•
When the oil drop is accelerating (up or down), there is a Fnet acting on the oil drop.
Using this theory, Millikan was able to calculate the charge on thousands of different oil drops.
In all of Millikan’s trials, he found that the charges on all oil droplets were a multiple of 1.60x10-19 C. So
he concluded that the charge on an elementary particle is 1.60x10-19 C.
Example 1
A 2.10x10-15 kg oil drop is placed in an electrical field of 4.45x105 N/C acting downwards. If the oil drop
has a positive charge of 1.92x10-18 C, what is the acceleration experienced by the oil drop in the
electrical field?
Example 2
An oil droplet with a mass of 9.80x10-16 kg is suspended between two horizontal parallel charged plates.
If the electric field strength between the plates is 2.0 x 104 V/m, what is the magnitude of the charge
on the oil droplet?
Example 3
An oil drop with a weight of 4.80x10-14 N is suspended between two horizontal parallel charged plates
that are placed 5.00cm apart. If the potential difference between these plates is 3.00x103V, how many
excess electrons does the oil drop carry?
Homework:
Page 763 #1,2
Pg. 764 #1,2
Pg. 765 #6
Physics 30
Atomic Physics – Model of the Atom (Bohr, Quantum)
Name: ____________________
Date: _____________________
Continuous Spectrum
Neils Both studied the spectra
that was produced from a hydrogen
atom, which helped him develop his
theory of the atom to overcome
Rutherford’s shortcomings. From
previous scientists, Bohr knew that if
you shone white light through a prism
or a diffraction grating, light would
be dispersed (separating white light
into its individual wavelengths). The
rainbow pattern that is produced
(where one colour continues into the
next) is called a continuous spectrum.
Bohr decided to [pass white light
from a glowing object through an
unexcited has (gas that is cooled and
has very little energy) first and then
through a prism or grating.
Absorption Spectrum
Bohr observed that the same continuous spectrum was produced, but
it had dark lines appearing in the spectrum. Those dark lines meant
that those particular photons with specific frequencies/
wavelengths/energies were missing from the spectrum.
Note: Recall that the energy, wavelength, and frequency of a photon
are all related as explained by the following equation
ℎ𝑐
𝐸 = ℎ𝑓 =
𝜆
This continuous, rainbow pattern with dark bands was termed a dark line spectrum or a line-absorption
spectrum. Bohr concluded that the unexcited gas must only be able
to absorb certain photons and not the entire spectrum, this
supports Planck’s hypothesis that matter is quantized.
Line Emission Spectrum
Bohr modified the experiment slightly and passed light given from a
glowing/excited gas (gas that is energized by some form such as
heat or electrical energy) through a prism or grating. This time,
Bohr observed that no continuous spectrum was produced, but only
thin bands of certain colours/(frequencies/wavelengths/energies)
were produced.
o
o
This spectrum was called a bright line spectrum or a line emission spectrum
Bohr concluded that the excited gas must only be able to emit certain photons, just as
cooled gas can only absorb and emit certain photons
Both atomic spectra (line absorption and line emission) help Bohr explain that atoms of a particular
element can only absorb and emit photons with certain frequencies/wavelengths/energies. If an element
can only absorb certain photons, it makes sense that the same element can only emit those same photons
Bohr also discovered that every element has its own unique atomic spectra
Bohr needed to revise the model of the atom to explain why matter is quantized and can only absorb or
emit certain photons. He proposed that within the atom, there are certain allowed energy orbits around
the nucleus, in which the electrons can move and orbit without giving off energy.
o This meant that the energy of the electron in an atom is quantized (just as Planck
hypothesized).
o For the electron to occupy any one of the allowed energy orbits, it must possess the
energy allowed for that orbit; electrons cannot be found between orbits.
o When an atom absorbs a photon, the electron in the atom will move up to a higher energy
orbit. An atom absorbing a photon corresponds to a dark-line absorption spectrum.
o When an atom emits a photon, the electron in the atom will move down to a lower energy
orbit. An atom emitting a photon corresponds to a bright-line emission spectrum.
Bohr developed energy level diagrams to help explain his model of the atom. The energy levels in Bohr’s
model are not equally spaced and will vary for each element.
Calculations using Bohr’s model are based off the conservation of energy:
Example Use following information to answer the next 5 questions
1. Determine the energy of a photon absorbed/released as an electron makes a transition from D to B.
Is the photon absorbed or released?
2. Determine the number of photons of different wavelengths that could possibly be produced due to
an electron at level C moving to ground state.
3. Determine the frequency of the photon absorbed/released when the electron in the atom moves
from C to A. Is the photon absorbed or released?
4. Determine the wavelength of a photon required to ionize an electron that was initially in ground
state. Is the photon absorbed or released?
5. An electron in ground state in the atoms is struck by a passing electron having an energy of 9.0eV
and the atom’s electron absorbs as much of the energy as possible. Determine the kinetic energy of
the passing electron after it collides with the electron in the atom.
Homework: Pg. 778 #1,2
Pg. 780 #6, 8, 11
(see pg. 776 for energy levels of hydrogen)
Physics 30
Atomic Physics – Quantum Mechanical Model
Name: ____________________
Date: _____________________
The Quantum Mechanical Model was developed by Heisenberg and Schrodinger, based on the probability
and waves.
1. Electrons behave as waves, in that they do not have
precise location or path.
2. Probability patterns called orbitals, can be visualized
as electron clouds (denser in areas of high probability).
3. Electrons can only exist in stable orbits if the
circumference of orbit is a whole number multiple of
the de Broglie wavelength. This creates a standing
wave pattern (constructive interference).
Heisenberg’s Uncertainty Principle
The location of an electron could be found more accurately by using ___________________
wavelength photons to irradiate it. This means increasing the _________________ of the photons
(p=h/λ). The electron will the be given ________________ by the _________________ (collision),
making its position more difficult to detect (alters the path). Thus, we cannot measure both the position
and the momentum of the electron with unlimited accuracy.
Physics 30
Atomic Physics – Nuclear
Name: ____________________
Date: _____________________
Nuclear Terms and Notation
Protons: positively charged particles found in the nucleus of the atom
o The number of protons determines the element type
o In a neutral atom, the number of protons is equal to the number of electrons
o The atomic number (Z) is the number of protons in the nucleus of an atom
Neutrons: neutral particles found in the nucleus of the atom
o The neutron Number (N) is the number of neutrons found in the nucleus of an atom
Atomic Mass/Mass Number (A): the total number of protons and neutrons in an atom because the
neutrons and protons are the most massive component of an atom
o Nucleons is another term for protons and neutrons in an atom’s nucleus
o The atomic mass number is usually indicated as a number attached to the back of an element
name (i.e. carbon - 14)
Isotopes: atomic nuclei that have the same number of protons but different number of neutrons
o Example: carbon – 12, carbon – 13, carbon – 14
Examples
1. How many neutrons are contained in a gold nucleus
2. How do the nuclei
12
13
6𝐶 , 6𝐶 ,
and
14
6𝐶
197
79𝐴𝑢 ?
differ? How are they the same?
Nuclear Reactions – Natural Trasnmutations
A nuclear reaction is a reaction in which one element is converted into another element. A nuclear
reaction is also a transmutation or nuclear/radioactive decay. The parent element is the original/initial
element in the nuclear reaction and the daughter element is the element produced in the nuclear
reaction.
A nuclear reaction is different from a chemical reaction because a chemical reaction just involved atom
rearranging, not atoms of one element converting into a new element
Examples:
Chemical Reaction: 2𝐶8 𝐻18 + 2502 → 16𝐶𝑂2 + 18𝐻2 𝑂
Nuclear Reaction:
13
6𝐶
+ 42𝐻𝑒 →
16
8𝑂
+ 10𝑛
There are many types of nuclear reactions, but all nuclear reactions are governed by the conservation of
charge (principle #7) and the conservation of mass/nucleons (principle #8).
Example: A uranium – 235 nucleus absorbs a neutron and then splits into a bromine – 87, three neutrons,
and one other daughter element. What is the unknown daughter element produced by this reaction?
Most nuclear reactions give off one or more of the following types of radiation:
1. Alpha radiation
2. Beta radiation
3. Gamma radiation
Alpha radiation
An alpha particle is a helium atom
To produce/release an alpha particle, the parent nucleus/element must lose/release two protons and two
neutrons
Example: Write out the alpha decay of uranium – 238
Beta Radiation
1. Beta-Negative (𝜷− ) decay
A neutron in the nucleus is transformed into a proton, and in the process emits an electron and an
extremely small neutral particle known as antineutrino (𝑣̅ )
• An electron is a beta-negative (𝛽 − ) particle and has no significant mass when compared to a
neutron or proton
Example: Write out the 𝛽 − decay for lead – 212.
2. Beta-Positive (𝜷+ ) decay
A proton in the nucleus is transformed into a neutron, and in the process emits a positron and a neutrino.
A positron (e+) is the antimatter/antiparticle to an electron and ahs the same mass and charge magnitude
as an electron, but just the opposite charge.
• A positron is a beta-positive (𝛽 + ) particle and has no significant mass when compared to a neutron
or proton
A neutrino (v) is an extremely small neutral particle and is the antimatter/antiparticle to the
antineutrino.
Example: What isotope will 𝛽 + decay of thallium – 202 produce? Write out the process.
Gamma (𝜸) Radiation
Most nuclear reaction are accompanied by the release of energy in the form of a gamma ray. Recall that
a gamma ray is just a high energy photon (a bundle of energy) from the EMR spectrum. Gamma radiation
is not a nuclear reaction/transmutation by itself as one element is not converted into another, energy is
simply being released.
Note: A series of nuclear reactions required to produce a stable, non-radioactive isotope is referred to
as a radioactive decay series (or chain).
Homework: Pg.799 #1-3,
Pg.800 #1-3
Pg.803 #1(top), 1a(bottom)
Pg.805 # 1a,b
Physics 30
Atomic Physics – Half-Life
Name: ____________________
Date: _____________________
Half-life: the time required for one half of the radioactive nuclei in a sample to spontaneously decay.
The half-life is specific to the type of radioactive material (i.e. different elements each have
unique/different half-lives). The number of nuclei of the original radioisotopes (i.e. parent element) left
in a sample after a given amount of time can be calculated using the following equation
𝑵 = 𝑵𝒐 (
𝟏 𝒏
)
𝟐
Where,
N is the amount of radioactive material remaining after a given
period of time
No is the original amount of sample before decay started
n
𝒏=
𝒕
𝒕𝟏/𝟐
Where ,
is the number of half-lived that occurred over a given period
of time
t is the time elapsed
t1/2 is the time for once half-life
The amount of a radioactive material may be expressed in different unit (i.e. mass, number of atoms,
percent, decays/second, becquerels, counts per minute, activity, etc.), but as long as N and N o are
recorded in the same type of unit, the formula can handle any type of units.
Graphical Representation
Examples 1
Carbon – 14 has a half life of 5730 years. How much carbon – 14 will remain in a sample after 17190 years
if the original sample contained 15.6g of carbon – 14?
Example 2
Radium – 226 has a half-life of 1600 years. What percentage of a sample of radium – 226 will remain
after 8000 years?
Example 3
The half-life of a radioisotope is 2.5 y. If the activity of the original sample of this isotope was
3.2x103Bq, what would be its activity after 5.0 y?
Hazards of Nuclear Radiation
All types of radiation (alpha, beta, gamma and EMR) have hazardous effect on biological tissue. When Xrays are required, patients are shielded with lead vests. Radiation was the devastating aftermath of
such events including the Chernobyl meltdown and the WWll atomic bombing of Japanese cities.
The level of danger of exposure to radiation depends on several variables:
1. The amount of energy of the radiation: The more energy the radiation has, the more hazardous
it is. High energy particles or photons can cause genetic damage by altering DNA and lead to
development of cancers and harmful mutations.
2. Amount of exposure to radiation: More exposure to or large doses of harmful radiation
increases the amount of energy being absorbed by biological tissue, therefore making it more
hazardous.
• Activity: the amount of radiation produced in a given period of time. Activity dependends
•
on the stability and amount of the radioactive substance.
Small amounts of harmful radiation vs. large amounts of low risk radiation.
3. Ability to ionize biological tissue: Ionization occurs when an atom losses and electron/(s). Cells
can be damaged or killed when exposed to ionizing radiation, resulting in radiation sickness.
Safety can be improved when working with radioactive material or high energy EMR by:
1. Decreasing exposure time
2. Increasing distance between people and the radioactive material
3. Increasing the shielding used
Type of
Radiation
Nature of
Radiation
Alpha
Helium nucleus
Beta
High speed
electron/positron
Gamma
High energy
photon
Penetrating Ability
-Paper
-Cannot penetrate skin
-cardboard
-penetrates about 1cm into
the body
-metal
-penetrates right through
the body
Ionization Ability
Hazard
High
Low, unless
ingested
Moderate to low
Moderate
Low
High
Example 4
Ultraviolet radiation is a type of ionizing radiation. Is it also a type of nuclear radiation? Explain.
Homework:
Pg.813 #1,2
Pg.814 #1,2
Pg.817 #1-8
Physics 30
Atomic Physics – Fission & Fusion
Name: ____________________
Date: _____________________
Fission and fusion are specific types of nuclear
reactions, which can be used for nuclear power
plants They involve the splitting of a heavy
nucleus (A>120) by bombarding the atom by a
neutron from a particle accelerator. The atom
absorbs the neutron, making it highly unstable.
The atom breaks into 2 lighter nuclei, and
releases two or three neutrons which will
collide with other atoms forming a chain
reaction. This releases 10x the energy of
normal disintegration, 1,000,000 x that of
chemical reactions. The reaction is controlled
with control rods which absorb neutrons.
Nuclear Fission
Nuclear Fusion
Definition
Fission is the splitting of a large
atom into two or more smaller
ones
Fusion is the fusing of two or more lighter
atoms into a larger one.
Requirements
for the
Reaction
Parent element needs a critical
mass and a high speed neutron is
required. However, very little
energy is required to split atoms
in a fission reaction.
High density and high temperature environment
required. High density required so high
probability small particles will collide and fuse
together. Extremely high energy is required to
bring two or more protons close enough and
overcome the electrostatic repulsion.
Energy
Released
The energy released by fission is
a million times greater than that
released in chemical reactions;
but lower than the energy
released by nuclear fusion.
The energy released by fusion is three to four
times greater than the energy released by
fission.
Natural
Occurrences
Fission does not normally occur in
nature. It is a man-made reaction
used in atomic bombs and nuclear
power plants.
Fusion occurs in stars, such as the sun.
By-Products of
the Reaction
Fission produces many highly
radioactive particles.
Few radioactive particles produced from fusion.
Mass-Energy Equivalence
Einstein concluded that there was a relationship between mass and energy and explained that mass could
be converted into energy and vise-versa. This theory is known as the mass-energy equivalence and can be
described by the following equation.
Where,
∆E is the change in energy (J)
∆𝑬 = ∆𝒎𝒄𝟐
∆m is the change in mass (kg)
C is the speed of light (3.0 x 108 m/s)
Example 1
What is the energy equivalence of a neutron at rest?
The theory of mass-energy equivalence is used to help explain why nuclear reactions, such as fission and
fusion, release so much more energy than a chemical reaction. Recall that all nuclear reactions are
described by the conservation of mass/nucleons.
Example:
4
2𝐻𝑒
+ 147𝑁 →
17
8𝑂
+ 11𝐻
•
When using standard nuclear notation, the units for atomic mass (A) are in atomic mass units (u).
•
1u = 1.66 x 10-27 kg
•
When using atomic mass numbers in the conservation of nucleons, these values are rounded to the
nearest whole number
•
On a smaller and more accurate scale, the total mass of all reactants in always greated than the
total mass of all products in all nuclear reactions
•
This difference in mass is know as the mass defect (∆m) and it is this “missing mass” that is
converted into energy according to the mass-energy equivalence theory, explaining why nuclear
reactions can release so much energy.
Example 2:
Radium-226 will undergo alpha decay
a) Write out this nuclear reaction
b) The atomic masses are 226.025410u for radum-226, 222.017578u for radon-222, and
4.002603u for an alpha particle. Calculate the mass defect.
c) Calculate the energy released by this nuclear reaction.
d) Calculate the energy released per nucleon for this nuclear reaction.
Particle-antiparticle annihilation occurs when two particles collide, causing the total destruction of
each particle and transforming all of their mass into energy according to the theory of mass-energy
equivalence (∆E = ∆mc 2). Recall that the antiparticle has all the same characteristic and physical
properties as the particle, but one physical property is the opposite.
Example 3:
Calculate the energy that is produced when an electron-positron pair annihilate.
Homework: Fission & Fusion Worksheet
Physics 30
Atomic Physics – Particle, Tracks, Antimatter
Name: ____________________
Date: _____________________
The model of the atom started out as a simple indivisible mass. It has now evolved to a complex theory
that contains multiple subatomic particles of extremely small size (ie. quarks, leptons, bosons, fermions,
mesons, hadrons, etc)! The standard model is the current theory that is used to describe the nature of
matter/atoms in terms of 12 fundamental particles (quarks, leptons, and bosons) and the fundamental
forces. The forces/interactions between all particles is based on the four fundamental types of forces.
FORCE
DEFINITION
RANGE
Strong nuclear
The force that holds the nucleus and quarks
Nuclear size
Electromagnetic
The force of attraction or repulsion between charged particles
Infinite
Weak nuclear
The force that allows the transmutation of quarks involved in
beta negative and beta positive nuclear reactions
Nuclear size
Gravitational
The force responsible for the attraction of two masses
Infinite
In order for physicist to have been able to break neutrons and
protons down into smaller subatomic particles, extremely large amounts
of energy was needed to overcome the strong nuclear forces that were
holding the nucleus and the quarks together. This is the reason particle
physicists collided atoms with each other at very high speeds in order to
overcome the strong nuclear forces and break the atoms down into their
subatomic particles. The development and
use of the Hardon Collider in Switzerland.
Not only did particle physicist need
to be able to break the atom down into
subatomic particles, they also needed
some way to detect such same particles. Scientists use bubble and cloud
chambers to track the path of small subatomic particles released after a
collision.
A cloud chamber contains dust-free air supersaturated with
vapour from a liquid such as water or ethanol and a bubble chamber
contains a liquefied gas on the verge of boiling. As a charged particle
speeds through the chamber, either the charged particle will cause the
vapour in a cloud chamber to condense into droplets or cause the
liquefied gas in a bubble chamber to vapourize into gas bubbles. Either
way, the charged particle leaves behind a track.
*Note: neutral particles do not leave tracks in could or bubble chambers!*
An external magnetic field is applied to these chambers to cause the charged particles to move in a
circular path, which is useful for helping physicists to determine what type of particle left that
particular track.
Example 1:
The picture below shows the tracks left behind from a proton, electron, and a positron. Identify the
path from each particle.
Example 2:
List 3 types of subatomic particles that do not leave tracks in a bubble chamber.
Example 3:
Describe and explain the difference in the tracks made in a bubble chamber by the particles in each
pair:
a) Protons and alpha particles
b) Protons and electrons
Homework:
Pg.834 #1,2
Pg. #2-5
Pg. 839 #3, 4, 6, 8
Physics 30
Atomic Physics – Quarks
Name: ____________________
Date: _____________________
Of the subatomic particles that was discovered and is a basic building block in the standard model is a
quark. Quarks are subatomic particles that have fractional charges (ie. charges less than the elementary
charge)
Name (Flavour)
Charge
Up (u)
+2/3 e-
Anti-up (u
̅)
-2/3 e-
Down (d)
+1/3 e-
̅)
Anti-down (d
-1/3 e-
Combinations of quarks make up protons and neutrons based on the conservation of charge.
• Stable matter (such as neutrons and protons) can only be composed of up and down quarks (no
antimatter).
• Unstable matter contains at least one anti-quark.
Quark composition of a proton and neutron based on the conservation of charge
Explaining Beta Decay
Beta Negative Decay
Beta Positive Decay