Chapter 9: Nuclear Changes
Section 1:
What is Radioactivity?
You have certainly heard the term
“radioactive” before. What does it mean?
Definition: radioactive atom –an atom with
an unstable nucleus.
• Things that are radioactive are often
thought of as being dangerous and
deadly.
– That is a pretty accurate assumption.
Unstable? What does that mean?
When an atom becomes unstable, it begins
losing its protons, neutrons, or electrons.
• Definition: nuclear decay – the loss of an
atom’s protons, neutrons, or electrons.
•Nuclear decay can cause an element to
become an isotope or an brand new element.
• When an atom gains or loses neutrons, it
forms an isotope.
– Definition: isotope – an atom that has
changed it’s number of neutrons (but not
protons).
For example:
• Hydrogen as an atomic mass of 1, and an
atomic number of 1.
– It has (1 – 1 = 0) neutrons.
– Deuterium, which is an isotope of
hydrogen, has an atomic mass of 2.
– It has (2 – 1 = 1) neutron.
– That is really all you need to know about
that.
Nuclear radiation is the product of decay:
• Definition: nuclear radiation – the
particles & energy released during
nuclear decay.
• Substances that give off nuclear radiation are
described as ‘radioactive’.
•There are 8 naturally radioactive
elements:
–Uranium (U)
–Radium (Ra)
–Radon (Rn)
–Francium (Fr)
–Polonium (Po)
– Protactinium
– Actinium
– Astatine
• Nuclear radiation can pass through any
state of matter.
• There are several different types of
radiation, depending on which particle is
being emitted.
We’ll start with the weakest type of
nuclear radiation: Alpha.
• Definition: alpha particle – nuclear
radiation composed of 2 p+ and 2
neutrons (a helium nucleus).
– It has a pos. chg. & is the
weakest type.
•It can be stopped by
paper or clothing (or skin).
Next up are Beta Particles.
• Definition: Beta Particles – nuclear
radiation composed of e-.
– Beta radiation is more powerful than alpha
& has a – chg.
– It can be stopped by thick wood or
aluminum.
Gamma Radiation
• Definition: gamma ray – nuclear radiation
composed of pure energy.
– Gamma radiation is the most powerful.
– Gamma radiation must be stopped by
lead or thick concrete.
Gamma radiation will NOT turn you into the Hulk.
• Marie Curie and her husband Pierre did
extensive gamma ray research.
The couple did extensive work and research
on gamma rays.
– They were awarded a Nobel Prize in Physics
for their work.
Unfortunately, their research had a high price.
– Due to exposure to gamma radiation, Marie
curie developed leukemia and died.
However, her research
revolutionized the science of
Physics, and has made current
cancer treatment possible.
Chapter 9: Nuclear Changes
The FISSION Bomb
Solar FUSION
Section 2:
Nuclear Fission & Fusion
What holds the nucleus of an atom
together?
• Definition: strong nuclear force – the
force that holds the particles of the
nucleus together.
– The strong nuclear force is greater than the
force that tries to push the protons away.
• Strong nuclear force causes atoms to be
stable, which don’t lose particles.
– But, when the force is NOT strong with an
atom, then you have…
•Weak Nuclear Force!
– Weak nuclear force causes atoms to decay.
Nuclear Fishin Fission
• Definition: nuclear fission – a process
that splits an atom’s nucleus into many
parts.
– The products of fission are elements that
are lighter than the original.
• Uranium is unstable, and undergoes
fission easily.
– Whenever this happens, uranium splits into
2 new elements.
– Barium and Krypton
Fission y’all!   
• Uranium is # 92
– Barium is #56 & Krypton is #36.
The opposite of fission is fusion.
• Definition: fusion – a process that joins 2
nuclei together to make a new element.
– The product of fusion is an element heavier
than the original.
• Both fission and fusion release large
amounts of energy.
– Nuclear fusion is how the sun produces its
energy.
– Nuclear fission powered the first atomic
bombs.
Chapter 9: Nuclear Changes
Section 3:
Nuclear Radiation Today
Where is Radiation?
• Nuclear radiation exists all around us…
• Definition: background radiation – nuclear radiation
that exists naturally in the environment.
• Background radiation is found in:
–
–
–
–
–
Soil
Rocks
Plants
Sunlight
Background radiation is weak enough so that it does not
harm living things.
Measuring Radiation
• Radiation absorbed by the human body is
measured in “rems”.
• Definition: rem – a unit of measuring the
amount of nuclear radiation absorbed by the
human body.
– The safe standard for nuclear radiation exposure per
year is 5 rems (or 5000 millirems).
Not-So-Natural Radiation
• Most natural radiation comes from inhaling
radioactive radon found in the environment.
• Smoking greatly increases your exposure to
nuclear radiation:
– Smoking 1.5 packs of cigarettes per day gives you a dose
of 8000 millirems per year.
Benefits of nuclear power…
• Tiny amounts of radioactive materials are
present in smoke detectors.
– The radiation emitted by the devise allows it to
detect when smoke is in the air.
Benefits of nuclear power…
• CT Scanners and PET scanners are used to
view internal organs and detect diseases.
Benefits of nuclear power…
• Nuclear radiation therapy is used to treat
cancer.
– Radioactive substances can be injected into the
body in chemotherapy…
Uses of nuclear power…
• Gamma rays can be passed through to body
to kill cancer cells.
The rest of the patient’s body is covered in
lead to protect it from the gamma
radiation.
Radiation Sickness
• If the body absorbs too much radiation, then
radiation sickness will occurs.
• Definition: radiation sickness – the condition caused
by excessive exposure to nuclear radiation.
– The sickness may occur from one large dose, or many
smaller doses over time.
Nuclear Power Plants
• Definition: nuclear power plant – a facility
designed to generate electricity using nuclear
fission.
Inside the power plant,
nuclear reactors use
Uranium to cause fission
reactions.
Nuclear Waste
• Nuclear power plants produce nuclear waste,
which is very radioactive.
– This waste must be buried underground in
concrete containers.
Disposal
Today, nuclear energy has many uses that
are NOT harmful or deadly.
• Today:
– Nuclear fission is used to produce
electricity.
– Nuclear radiation is used to treat diseases.
– Nuclear power is used in submarines.