Radioactivity

Fuel

• A substance that provides a form of energy

• The energy released is a result of changes to either the chemical or nuclear structure of the fuel

Chemical Reaction

Change in chemical structure of fuel (combustion)

Nuclear Reaction

Change in nuclear structure of fuel

Fossil Fuels

• Energy rich substances formed from the remains of once-living organisms

• Coal, oil, and natural gas

• Made up of hydrocarbons (carbon, hydrogen, and oxygen)

• When we burn a hydrocarbon (fossil fuel) in the oxygen of the atmosphere (combustion reaction), carbon dioxide and water are produced.

• In this process, energy is released (mostly in form of heat).

• We then harness this heat and convert it to other forms such as electricity (in power plants) or mechanical energy (in cars).

Nuclear Fission

• The process of uranium releasing energy (it is a very radioactive element).

• It can result in a violent explosion such as an atomic bomb, or a peaceful release of energy (nuclear power plant)

Protons

Positive particle, make up the nucleus

Neutrons

• Make up the nucleus of the atom

• Subtract atomic mass from atomic number to find out the amount of neutrons in an atom.

Electrons

• Negative charge

• Orbit the nucleus

• Have almost no mass

• Same number of electrons as protons

Atomic Number

Number of protons (found at the bottom of the element)

Atomic Mass

Total number of protons plus number of neutrons (found on the top of the element)

Isotopes

• Different types of one element

• Only differ by number of neutrons

• Number of protons remain the same

What makes an element more radioactive than others?

The higher the difference in the number of protons versus the number of neutrons, the more radioactive the element is.

Nuclear Fission

• Uranium dissociates (decays) and releases energy, by receiving a stray neutron!

• In each single fission process, tiny amount of mass disappears and is converted to energy (E = mc2), thus tremendous amount of energy is releases!

• One neutron starts the fission process. At the end of the first step, three neutrons are generated. This is an exponential growth for number of neutrons.

• This process has a chain reaction and continues on its own. That is why it has potential to continuously radiate.

• Nuclear fission harnesses energy in power plants.

Radioactive Elements

• Any material with a natural tendency to dissociate to lighter elements.

• E.g. Uranium, Cobalt, Plutonium, Radon

Radioactivity

• When radioactive element undergoes nuclear reaction, it emits energetic particles (Alpha and Beta particles) as well as heat in form of Gamma rays!

• The most important differences of these radiations are their penetration power through materials.

Radioactivity in Equation

• When a radioactive elements undergoes several nuclear reactions over time, emitting particles and radiation, it turns into other elements in the periodic table.

• So, constantly, new elements are formed!

• As the nuclear process continues, amount of initial radioactive material left decreases over time in a neat fashion (decay).

• This process is completely random, but we can formulate it.

What is the half-life of carbon?

5730 years

Carbon Dating

• Carbon-14 is continuously generated in the higher levels of the atmosphere, causing every living organism to have a concentration of Carbon-14 in their body.

• Nitrogen-14 is forced to transform to Carbon-14 due to cosmic rays from the sun.

• This radioactive isotope of carbon enters the food cycles of living animals, and precipitates on soil/is taken by all living organisms every day.

• This cycle continues and the continuous uptake maintains a fixed concentration of this isotope in living beings.

Carbon Dating and Decay

• When dead, no more absorption of Carbon-14 takes place

• It begins its natural decay to Nitrogen-14

• The concentration of this isotope decreases over time