Rocco DiVerdi and Dylan Martin
Radioactivity page 1
Table of Contents
Periodic Table 2
What is an Atom 3
Discovery of Radioactivity 4
Origins of Radiation 5
Forms of Radiation 6
Carbon Dating 7
Radioactivity in Biology 8
Radioactivity in Medicine 9
Cleaning with Radioactivity 10
Atomic Bombs and Nuclear Reactors 11
Atomic Bombs Type 1 12
Atomic Bombs Type 2 13
Nuclear Reactors 14
Radioactive Catastrophes 15
Radioactive Waste 16
Everyday Radioactivity 17
About the Authors 19
Image Credits 20
Radioactivity page 2
The Periodic Table
The periodic table is the means by which scientists have
organized all of the known (and even some unknown!) elements. The
table is organized by increasing amount of protons found in an
element, an atomic attribute also called atomic number.
atomic number of the elements in this table increases from left to
right and down.
The elements are also ordered based on the
arrangement of electrons
in the atom and
properties shared by
various elements. Stable,
non-charged atoms have
the same number of electrons as
The periodic table of elements.
protons, and often have a similar quantity of neutrons.
Radioactivity is most often seen in so-called heavy elements that
are found largely as synthesized atoms in laboratories. A lack or
surplus of neutrons in an isotope of an element may also result in
instability and radioactivity.
DID YOU KNOW?
Scientists researching new elements are currently searching for what they call the island of
stability. Modern chemists hypothesize that a group of elements with extremely high atomic
numbers will be found that are stable. This set of elements has not yet been found, and all
atoms with greater than 92 electrons exist only briefly before undergoing decay.
Radioactivity page 3
What is an Atom?
Atoms are the most basic form of an element that retain the
same properties and features as the element as a whole.
base elements of matter are formed from three types of subatomic
particles: protons, neutrons, and electrons.
protons and neutral neutrons are found in the dense innermost
section of the atom known as the nucleus. The number of protons
found in an atom defines the element, but different numbers of
neutrons may be present. Atoms of the same element with different
numbers of neutrons are known as
This part of the atomic
structure accounts for nearly 100
percent of the mass of the atom.
Electrons are significantly less
massive than the other subatomic particles, and they circle around
the nucleus in different levels, called shells. These negatively
charged particles and their behavior is the cause for the majority
of the chemical properties of an atom. This designation of atomic
properties encompasses how the components of an element interact
with other atoms.
Radioactivity page 4
The Discovery of Radioactivity
In the early twentieth century, Marie Currie, a Polish
chemist and physicist pioneered the study of radioactivity.
Partnered with her husband,
Pierre Currie, she developed the
basic theory of this phenomenon,
found new methods to isolate
radioactive isotopes, and
Marie Curie in the laboratory with her
discovered two elements: polonium
and radium. Curie began her studies in this field as she searched
for a topic for a thesis paper. In previous research, an earlier
scientist, Henri Becquerel, found that uranium emitted rays
similar to X-Rays without the input of an external energy source,
and Marie looked more deeply into this seemingly inexplicable
occurrence finding that the presence of uranium caused the
surrounding air to conduct electricity, and that the conductivity
of the air depended on the quantity of uranium present.
received many awards and honors, including two Nobel Prizes for
Radioactivity page 5
Origins of Radiation
Heavy radioactive elements have so many protons and neutrons
in their nucleus that they become unstable.
The protons, which
have positive charges,
repel from each other
with a greater force
than the forces holding
the atoms together, so
the atoms tear
Particles being released from an atom
Electrons, neutrons, and protons break away from the atoms at
extremely high velocities and become radiation. The three types of
radioactivity, Alpha particles, beta particles, and gamma rays,
are made up of these subatomic particles which have been released
DID YOU KNOW?
There are particles smaller than protons, neutrons, and electrons. Protons and neutrons are
made up of particles called quarks. There are only two types of quarks (up and down), and
different combinations of these make up protons and neutrons. Very little is known about
quarks. They seem to have the ability to appear and disappear randomly, as well as switch
between up and down quarks. These tiny particles are the next step for scientists seeking to
understand how the world works.
Radioactivity page 6
Forms of Radiation
Alpha particles are groups of protons and neutrons which,
once released, make up the nucleus of other elements (most
Beta particles are electrons which have been
emitted from the atom. Gamma rays are similar to light rays or x
rays because they are
made up of photons,
or packets of energy,
which are smaller
than any of the
atomic particles, and
which can pass
through solid matter.
The photons originate
Different radioactive particles released from
in the nucleus of the atom, near the protons and neutrons, then
exit at the speed of light. Gamma rays are the most dangerous of
the particles of radiation because they can pass through cells and
tissues, causing mutations.
Radioactivity page 7
Carbon dating, or radiocarbon dating as it is sometimes
called, allows researchers to estimate the age of objects up to
62,000 years old using radioactivity. This dating process is
based on the radioactive isotope carbon-14 (this notation means a
carbon atom with fourteen neutrons) and its process of decay.
Atoms of this isotope have a half-life of 5,730 years, meaning
that the fraction of carbon-14 in a given sample will decrease by
half in this period of time. With
this knowledge, scientists can
calculate the approximate age of
an object that contains this
isotope based on the amount that
is currently present. This
scientific advancement has had a
very important impact on humans’
Ötzi the Iceman, a natural mummy that was
carbon dated and found to live in
approximately 3300 B.C.E.
understanding of history.
DID YOU KNOW?
Some of the most famous documents and objects in the world have been carbon dated. This includes
the Dead Sea Scrolls, which are early transcripts of various Bible passages, the Shroud of Turin,
a collection of Ancient Egyptian artifacts that have allowed researchers to create a timeline for
the dynasties of Egypt, and Ötezi the Iceman, the remains of an early human found in the Alps on
the border of Austria and Italy
Radioactivity page 8
Radioactivity in Biology
Using radioactive forms of common elements, scientists can
discover how organisms use those elements to help them live.
radioactive form of an element can be substituted for the normal
form of that element in any chemical reactions, so the radioactive
element can move throughout that plant
or animal in the same way as the nonradioactive
form. By tracking where the
radiation moves throughout the organism,
scientists can find out what those
elements do for the organism.
process was used to prove that DNA
carries genetic information from parents
to their children. An element in the DNA
of a virus was replaced with the
radioactive form of the same element.
The virus replaced the DNA in a cell,
Radioactive DNA is
transferred from parent
virus to children viruses
Radioactivity page 9
causing the cell to make more viruses.
Because the new viruses
were shown to be radioactive, the experiment proved that DNA
carried the genetic information.
Radioactivity in Medicine
Radioactivity has many applications in the medical field,
ranging from its use in treatment methods for various diseases to
most common medicinal implementations of this chemical occurrence
and is often used to treat cancer and kill malignant cells in the
body. The form of radiation used in this process is an effective
The machine used to
send X-rays through an
object, creating an
means by which doctors can limit cell growth,
thus combating the dangerous symptoms of
cancer. Radiation therapy may also be coupled
with chemotherapy to combat more aggressive
and widespread cancers. Radiology, the
practice of employing radiation to image the
human body and diagnose disease, is another use
of radioactive decay in the medical field. This medical specialty
encompasses the use of X-Rays to image the musculoskeletal system
and various other imaging technologies including CT scans,
magnetic resonance images (MRIs) and ultrasounds.
Radioactivity page 10
Cleaning with Radiation
Radiation is generally considered to be very dangerous
because of radiation poisoning and increased risks of cancer which
can result from direct exposure to radioactivity.
properties which make radioactivity dangerous, however, can also
be used to make things safer. In the correct amounts, radiation
can be applied to food or even sterile lab equipment to remove any
these processes, the
pass through the food
A strawberry being disinfected by Gamma Rays
or equipment, killing
any small organisms, but the radioactive elements stay far away
from the sterilized object to avoid any potential for it to become
By controlling the amount of radiation, small
bacteria inside of foods can be destroyed while the food itself
Radioactivity page 11
Atomic Bombs and Nuclear Reactors
In both atomic bombs and nuclear reactors, radioactive
elements are forced to release radioactivity at a much faster rate
than they otherwise would. When critical mass is reached, meaning
when too much radioactive material is very close together, the
released from one atom
hit other atoms,
causing those atoms to
The chain reaction that occurs when radioactive
elements reach critical mass
of their own. With enough radioactive particles knocking other
particles loose, a chain reaction starts, causing the radioactive
material to release incredible amounts of energy at one time. The
half-lives of the radioactive elements used in nuclear reactors
and nuclear bombs are millions or even billions of years.
nuclear explosion, all of the energy that would have been slowly
released over extremely long periods of time is released at once.
Radioactivity page 12
Atomic Bombs Type 1
Atomic bombs begin uncontrolled, extremely rapid chain
reactions of nuclear material.
There are two types of atomic
bombs, but both rely on generating a critical mass of radioactive
substance so that an atomic chain reaction can begin.
design, there are two sections of radioactive material.
one is at critical mass by itself, so before the bomb is
detonated, there is no risk of an explosion.
To detonate the
bomb, small explosives are used to fire one of the pieces of
radioactive material into the other piece, so that the pieces
together achieve critical mass.
Radioactivity page 13
Atomic Bombs Type 2
The other type of atomic bomb begins with only one piece of
radioactive material. It is not at critical mass, so there is no
risk of an accidental explosion, but no more material is added to
generate critical mass.
Instead, explosives all around the bomb
compress the radioactive material together.
This increases the
density of the radioactive material, meaning that all of the atoms
get closer together, just like how the
two blocks of material got closer
together in the first type of bomb.
When the atoms get closer together, it
becomes easier for the small radioactive
particles to hit other atoms, so the
A diagram of the implosion
style atomic bomb
chain reaction can begin. Even though the amount of radioactive
material does not change, critical mass is still reached.
DID YOU KNOW?
Before the atomic bomb was finished in World War II, members of the Manhattan project, the
team assigned to develop an atomic bomb, created the first nuclear reactor in a Chicago
football stadium. Their goal, however, was to build a bomb, so there was no further
experimentation on using nuclear reactions for power until after the war. Even then, nuclear
reactors were developed for military use. One of the first uses of nuclear power was for a
submarine powered by a nuclear reactor, a concept that is still used today.
Radioactivity page 14
Nuclear reactors use the same principle as atomic bombs, but
instead of starting an uncontrolled reaction, the chain reaction
is watched carefully.
To start the reaction, two pieces of
radioactive material are moved toward each other, then held at a
certain distance so that there is a
chain reaction between the two
pieces of radioactive material, but
that chain reaction maintains a
constant speed instead of
increasing speed as it does in a
reactors, there are many safeguards
to ensure that the chain reaction
A picture of the inside of a
remains under control.
There are both people and computers
monitoring the reactors at all times, and there are built in
failure points which will stop the reactor before an explosion
DID YOU KNOW?
The sun, as well as all other stars, is actually a naturally occurring nuclear reactor.
There is radioactive material at the core of the sun which continually reacts, generating
heat, fire, light, and radiation. When a star runs too low on radioactive material, it
collapses on itself, generating critical mass with the material that is left, then explodes
in a supernova.
Radioactivity page 15
Although radioactivity has many positive uses and
applications, it was extremely dangerous in earlier years. There
have been several highly public disasters involving radioactive
materials and their use that exemplify this danger.
and possibly most well-known of these, was the
accident at the Chernobyl nuclear reactor in
The explosion emitted radioactive
particles into the atmosphere, which spread
across Europe, causing disease and rendering
The Chernobyl power plant
the surrounding area uninhabitable. A similar
accident occurred in Pennsylvania in 1979 at the Three Mile Island
nuclear power plant. The results of this incident were not nearly
as significant as those at Chernobyl, but revealed the dangers of
this emerging power source to the American public.
radioactivity also arose at the blast sights of the atomic bombs
dropped on Hiroshima and Nagasaki, Japan during World War II,
where high levels of radiation caused a large number of deaths
Radioactivity page 16
well after the bombs were dropped.
Many processes that involve nuclear reactions produce
radioactive byproducts which must be treated and disposed of.
This waste poses a serious environmental threat due to its
Radioactivity does diminish over time due
to the decomposition of radioactive
elements, but if sizable quantities of
these byproducts were created regularly, it
would create large issues in attempting to
safely discard them.
The production of
The sign indicating the presence
of hazardous radioactive waste
such hazardous material is one of the major
sources of argument against the large-scale
use of nuclear power, which otherwise causes little ecological
damage. Researchers are currently researching effective means of
disposal for this waste.
Governments across the globe heavily
regulate the output and treatment of radioactive materials to
avoid the occurrence of any accidents or endangerment of the
The discovery of an effective treatment method for
radioactive waste would greatly advance the use of nuclear power
Radioactivity page 17
and other applications of nuclear reactions.
Radioactivity is often viewed as a complex and advanced
concept, but radioactive objects and events involving this
occurrence can be seen in everyday life.
Bananas, for example,
contain a significant, although not dangerous, level of radiation.
Nearly all organic matter contains
some radioactivity, although these
levels are negligible.
been some notable incidents involving
everyday individuals and
radioactivity, including that of the
so-called radioactive Boy Scout.
Bananas contain a significant
level of radiation
In 1994, David Hahn, a
seventeen-year-old Boy Scout, attempted to make a nuclear reactor
in his own home using thorium and lithium. Although his reactor
was never fully functional, it did emit dangerous radiation with
the potential to cause serious health complications.
government agencies became involved with the cleanup of this
Radioactivity page 18
project when it was discovered, and the property was deemed a
dangerous environment by the Environmental Protection Agency.
Atomic Number: The number of protons found in an atom
Subatomic Particles: The particles that compose all atoms
Protons: Positively charged subatomic particles found in the
nucleus of an atom
Neutrons: Uncharged subatomic particles found in the nucleus
of an atom
Electrons: Negatively charged subatomic particles found in
shells around the nucleus
Nucleus: The dense center of an atom containing protons and
Isotopes: Variations of atoms of a single element with
different numbers of neutrons
Half-life: The time it takes for half of a given amount of a
radioactive substance to decay.
The amount of a substance needed to cause a
Radioactivity page 19
About the Authors
Rocco DiVerdi is a senior at the
Massachusetts Academy of Math and Science.
His hobbies include building models and
working on robots. He plans on pursuing an
engineering degree in college after his senior
year at the Mass Academy, where he will be
taking freshmen classes at WPI.
Dylan Martin is also a senior at the
Massachusetts Academy. He will take freshmen WPI
classes next year, and will use that experience to
find his focus for college. He enjoys philosophy
and debate and is studying these topics as well as
biotechnology and calculus.
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