1. Radioactivity
Antoine Becquerel hypothesized that salts would glow after being exposed to light which produced X-rays while they glowed.
His experiment lead to the discovery of radioactivity.

2. Nuclear Decay
Radioactivity is the process in which an unstable atomic nucleus emits charged particles and energy.
An atom containing an unstable nucleus is called a radioactive isotope or radioisotope.
Carbon-14 is a common radioisotope.
When the composition of a radioisotope changes, the radioisotope is said to undergo nuclear decay.

3. Nuclear Decay Cont.
During nuclear decay, atoms of one element can change into atoms of a different element altogether.
Uranium-238 decays into Thorium-234.

4. Types of Nuclear Radiation
Nuclear radiation is the charged particles and energy that are emitted from the nuclei or radioisotopes.
Common types
Alpha particles
Beta particles
Gamma rays

5. Alpha Decay
Alpha particles is a positively charged particle made up of two protons and two neutrons.
He is the common symbol.
The product isotope has two fewer protons and neutron than the reactant isotope.
See example U.
Alpha particles are the least penetrating type of nuclear radiation.
Most travel only a few cm in the air and can be stopped by a sheet of paper or by clothing.

6. Beta Decay
Beta particles are the release of negatively charged radiation.
Electrons are emitted by an unstable nucleus.
During beta decay, a neutron decomposes into a proton and an electron.
The proton is trapped in the nucleus and the electron is released.
The product isotope has one more proton and one less neutron than the reactant isotope.

7. Beta cont.
Due to the smaller mass and faster speed, beta particles are more penetrating than alpha particles.
Beta particle can pass through paper but is stopped by a thin sheet of metal.

8. Gamma Decay
Gamma ray is a penetrating ray of energy emitted by an unstable nucleus.
Has no mass and no charge.
They are energy waves that travel through space at the speed of light.
During decay, the atomic and mass number remains the same, but the energy of the nucleus decreases.
Gamma rays are much more penetrating than alpha and beta particles.

9. Effects of Nuclear Radiation
You are exposed to nuclear radiation every day.
Most is background radiation, or radiation that occurs naturally in the environment.
When nuclear radiation exceeds background levels, it can be damage the cells and tissues in your body.
Exposure to nuclear radiation causes the bonds holding together proteins and DNA molecules can break.

10. Effects cont.
The changes causes the cells to no longer function properly.
Alpha particles can cause skin damage similar to a burn.
Alpha particles causes no serious health hazards unless inhaled or eaten.
Beta particles can damage tissues in the body more than alpha particles, but less than gamma rays.
Gamma rays can penetrate deep into the human body, exposing all organs to ionization damage.

11. Half-Life
Nuclear decay rates describes how fast nuclear changes takes place.
Half-Life is the time required for one half of a sample of radioisotope to decay.
After one half-life, half of the atoms in the sample has decayed, leaving the other half unchanged.
After two half-lives, half of the remaining half decays leaving one quarter unchanged.
The pattern continues.
Nuclear decay rates are constant.

12. Half-Life cont.
To figure out total half lives use the follow equation:
Half-lives elapse = Total time of decay/Half-life
One gram of iridium decay. The half-life is 15 minutes. After 45 minutes how much iridium will remain in the sample?
After three half-lives, the amount of iridium has been reduced by half three times.
After 45 minutes, gram of iridium remains while gram has decayed.

13. Radioactive Dating
In radiocarbon dating, the age of an object is determined by comparing the object’s carbon-14 levels with the carbon-14 levels in the atmosphere.
Radiocarbon dating has helped archaeologists learn more about ancient civilizations.