RADIOACTIVITY - the Scientia Review

RADIOACTIVITY - the Scientia Review


Rocco DiVerdi and Dylan Martin

Radioactivity page 1

Table of Contents



Contents 1

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

Glossary 18

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.


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.

Positively charged

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

husband, Pierre

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

this work.

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

from atoms.


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

commonly helium).

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

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.


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.

These same

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

harmful bacteria.


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

remains unaffected.

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

radioactive particles

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.

In a

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.

In one


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.


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

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

nuclear explosion.

In current

reactors, there are many safeguards

to ensure that the chain reaction

A picture of the inside of a

nuclear reactor

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

could occur.


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

Radioactive Catastrophes

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.

The first,

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.

Issues from

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.

Radioactive Waste

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

dangerous properties.

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.

Everyday Radioactivity

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.

There have

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.

Critical Mass:

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.

Radioactivity page 20

Image Credits



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