Chapter 9: Nuclear ChangesSection 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?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.

• 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

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

Section 2:Nuclear Fission & Fusion

The FISSION BombThe FISSION Bomb Solar FUSIONSolar 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.

• 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.

Nuclear Fishin Fission

• 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 ChangesSection 3:

Nuclear Radiation Today

• 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.

Where is 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).

Measuring 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.

Not-So-Natural Radiation

• 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…

Benefits of nuclear power…

• Gamma rays can be passed through to body to kill cancer cells.

Uses of nuclear power…

The rest of the patient’s body is covered in lead to protect it from the gamma

radiation.

• 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.

Radiation Sickness

• Definition: nuclear power plant – a facility designed to generate electricity using nuclear fission.

Nuclear Power Plants

Inside the power plant, nuclear reactors use Uranium to cause fission reactions.

• Nuclear power plants produce nuclear waste, which is very radioactive.– This waste must be buried underground in

concrete containers.

Nuclear Waste

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.