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The Nucleus. Compare the benefits and dangers of radioactivity. Which isotopes are used for treatments of which illnesses? How is background radioactivity different from natural radioactivity? How did the transuranium elements come into existence? Does fusion or fission produce more energy?

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The Nucleus

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The nucleus

The Nucleus

Nuclear concepts to master

Compare the benefits and dangers of radioactivity.

Which isotopes are used for treatments of which illnesses?

How is background radioactivity different from natural radioactivity?

How did the transuranium elements come into existence?

Does fusion or fission produce more energy?

What are the equations for fission and fusion?

Which reaction has not been achieved and which one is used in nuclear power plants (fission or fusion)?

Compare fission and fusion.

What is the shielding effect?

Write and balance equations that involve alpha, beta, neutron, positron, or proton particles and gamma radiation.

Which direction will alpha particles move when placed in an electric field?

What is the band of stability?

What is the difference between and artificial and natural transmutation?

Use table N and O to solve problems.

Solve problems involving half-life using the equation or the “walk-the-dog” method.

Half-life is constant!

What is a Geiger counter used for?

How do scientist use uranium isotopes to date rocks?

How do scientist use carbon isotopes to date mummies?

Why do doctors use radioisotopes with shorter half-lies when performing a medical procedure?

Which radioisotope is used for sterilizing things like medical equipment?

Which isotope is used in the irradiation of meat?

Nuclear Concepts to Master



Alpha particle

Artificial radioactivity

Background radioactivity

Beta particle


Daughter nucleus








Gamma radiation





Natural radioactivity


Penetrating distance


Radioactive isotopes





Transuranium elements



Radioactive decay of Uranium

Half-Life Simulation


Electromagnetic spectrum

Electromagnetic Spectrum

LESS harmful to the body

MORE harmful to the body

Ionization is the ability of an atom to become an ion (charged particle).

If electrons are lost a cation is formed.

If electrons are gained an anion is formed.

Ionization is the ability of an electron to jump away from or to another atom.

Ionizing power

Ionizing Power

  • The ionizing power of ionizing radiation measures how many ions are formed in a given area when the radiation passes through it.

  • It indicates how densely packed incidents of ionization will be. In human tissue ionization occurring in a limited location means concentrated tissue damage and will increase the probability of cell death or mutations due to DNA damage.



  • Unstable isotopes

  • To become more stable, the atom spits out subatomic particles and rays of energy

  • This release of subatomic particles and rays is radioactivity

31H = H31 =H3= H-3

Unstable nucleus

In the band of stability, atoms are stable. The ratio n/p  is 1 for low nuclear masses and it increases steadily up to 1.5 for high nuclear masses.

Unstable Nucleus?

In region A, a nucleus with too many neutrons is unstable because not enough of them are paired with protons.

In region B, a nucleus with too many protons has too much repulsive electrical interactions to be stable.




Map of u s natural radioactivity

Map of U.S. Natural Radioactivity

The colors indicate uranium concentrations: red is high, yellow is medium, blue is low.

Natural radioactivity

Natural Radioactivity

The earth is radioactive (air, water, and soil).

Due to elements that spontaneously and uncontrollably emit radioactivity.

Radioactive elements are also called:

Radioactive isotopes



The nucleus

Types of Radiation - Beta

  • A beta particle is like a fast electron.

    • It’s mass is small like an electron’s.

    • Since it’s small, it can penetrate your skin!

Beta Decay

Types of radiation positron

Types of Radiation - Positron

  • A positron  is an like an electron but with a positive charge!

    • It’s small like an electron

    • It has a charge of +1 (opposite to an electron!)

    • When it meets with an electron it annihilates it!

    • Often when nuclei that release positrons also release gamma radiation.

    • Can penetrate your skin!

Positron Decay

Types of radiation alpha

Types of Radiation - Alpha

  • An alpha particle  is a particle that is made up of two protons and two neutrons.

    • It is therefore a helium nucleus with a mass number of 4 and a atomic number of 2. 42He

    • It has a mass of 4.0 amu - massive on a nuclear scale!

    • Too BIG to penetrate your skin.

Types of radiation gamma

Types of Radiation - Gamma

  • The gamma ray  is a photon of high energy.

    • It has no mass.

    • It has no charge.

    • Can penetrate your skin!

  • For gamma ray emission to occur the nucleus must still be in an unstable state after emitting an alpha, beta or positron particle. So to become more stable, it spits out more energy.

Gamma radiation released with beta decay

Radiation in an electric field

Radiation in an Electric Field




The nucleus

Try # 5 – 9 on your own before clicking to get the answers.

The nucleus

These are often referred to a SHIELDS and they

Protect you from radiation. Distance is also a shield.

Artificial radioactivity

Artificial Radioactivity

  • Man-made

  • Stable isotopes are bombarded with particles such as neutrons to cause a nuclear reaction.

  • Elements with atomic numbers over 92 have been artificially made. They are called the transuranium elements.

  • (92 is the atomic number of the heaviest naturally occurring element, Uranium.)

  • Atom Smashers

  • Nuclear reactors

Fission larger nucleus is split into smaller nuclei mass is converted to energy

FissionLarger nucleus is split into smaller nuclei.Mass is converted to energy!

Control rods needed in nuclear power plants! WHY? It’s a CHAIN REACTION

The nucleus

FusionFusion is when two small nuclei combine to form a single bigger nucleus.Mass is converted to energy!



Produces hazardous waste since nuclear fuel rods last about 3 years.

The used rods are stored underground

As of 2000, the amount stored is 40000 metric tons


Little to no hazardous waste (He released and no reactor core)

Inexhaustible energy – 1 gallon of sea water contains enough deuterium to support a family of 4 for 1 year.





  • Effect of distance

  • Effect of shield

    • thickness

    • type



  • Shielding protects you from radiation exposure.

Determining the type of rxn

Determining the type of rxn

  • Absorption (Always Artificial)

  • Emission (natural DECAY)

  • Artificial transmutation

  • Natural Transmutation (DECAY)

  • Fission

  • Fusion

Half life of radioisotopes

The time taken for a given sample of a radioisotope to decay so that its radioactivity is one half the initial amount is called the half-life, t½, of that isotope.

The half-life is a constant for the isotope, and shows enormous variations from one isotope to another.

For example, 17F (fluorine-17) has a half-life of 70 seconds, while 238U has a half-life of 4.51 x 109 years. 14C (carbon-14) has a half-life of 5668 years.

The long-lived nature of some waste products of nuclear reactors pose grave ecological problems, as some of these radioisotopes remain dangerously active for tens of thousands of years.

Whereas the short-lived nature of some radioisotopes allow their use in medicine.

Half – Life of Radioisotopes

Rate of decay half life

Rate of Decay – Half Life

Rate of decay half life1

Rate of Decay – Half Life

What’s the half-life of Sr-90?

What type of curve is the above?

What would the graph look like if the

The y-axis was % being transformed?

Calculating half life

Calculating Half Life

How much 42K will be left in a 320 g sample after 62 h?

Step 1: Look up the half life in Table N, the table of Selected Radioisotopes

12.4 h

Step 2: Set up a table showing the mass, time elapsed, the fraction remaining, and number of half lives.

Step 3: Fill in the table with the starting condition(s) and ending when the full time has elapsed. Time will always start with 0. Fraction will always start as 1, and Half-lives will always start at 0.

Step 4: For each half life elapsed:

a) cut the mass in half

b) increase the time by an amount equal to the half life

c) cut the fraction in half

d) add one to the number of half lives

Calculating half life1

Calculating Half Life

Determining half life from a graph

Determining Half – Life from a graph

The table below shows how the activity (in counts per second) of a sample of radioactive material varies in time. Plot a graph of activity against time to determine the half-life of the material.


Extremely Beneficial

Nuclear power plants

Nuclear medicine

Cardiovascular imaging

Bone scanning

Detecting cancers

Extremely Dangerous

Nuclear power plants released radioactive substances into the atmosphere during nuclear accidents.

Three Mile Island


Nuclear Bomb


Radiological dating

Radiological dating

  • We can use the natural radioactivity in some objects to date them.

  • The following slide shows a rock containing naturally occurring radioactive uranium.

  • As time goes by, the uranium decays to stable lead.

  • By comparing the proportions of uranium and lead we can determine the approximate age of the rock.

Isotopes in medicine

Isotopes in Medicine

  • Nuclear medicine imaging techniques give doctors another way to look inside the human body. The techniques combine the use of computers, detectors, and radioactive substances.

  • It is very important to consider the half-life of a substance that is to be used for medical purposes.

Isotopes in medicine1

Isotopes in Medicine

  • Co-60

    • Beta and gamma emitter

    • Sterilization of medical equipment

    • Treatment of malignant tumors

  • I-131

    • Beta and gamma emitter

    • Iodine-131 is one of the radioactive isotopes of iodine that can be used to test how well the thyroid gland is functioning.

Co 60 and meat

Co-60 and Meat

  • food is irradiated in an area that is surrounded by concrete walls at least 6-feet thick which keep any rays from escaping.

  • The radiation source, usually Cobalt 60, is held in a resting position in a pool of water.

  • A conveyor system transports the meat or poultry product to the area.

  • The radiation source is then raised out of the water and the food is exposed for a defined period of time.

  • When the source is raised, lights and alarms are sounded to make people aware that the product is being irradiated.

  • Once the food is irradiated, the source automatically returns to the resting position and the food leaves the area for further processing.

Detecting radioactivity

Geiger Counter

Measures radiation as CPM

Counts per minute

the amount of radioactive material (counts) that is released in one minute

Film Badge

Radioactivity will expose film.

The amount of film exposed indicates the level of exposure to radioactivity.

Detecting Radioactivity

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