Radioactivity and Nuclear Decay Notes

Types of Radioactivity

Radiation

• Radiation, also known as nuclear radiation, refers to the particles or waves emitted by radioactive substances.

• An atom consists of electrons orbiting the outside and a central nucleus, made up of protons and neutrons.

• Nuclear radiation originates from the nucleus of a radioactive atom.

• In a radioactive atom, the nucleus is unstable and emits particles or waves to form a more stable atom.

• This process is called radioactivity or radioactive decay, and it is a natural and spontaneous process.

Radioactivity

• Radioactivity is the breakdown of an unstable element into another.

• This involves a "parent" element transforming into a "daughter" product.

• Some atoms of elements exist as radioactive isotopes.

• Example: Carbon-14 is a radioactive isotope of regular carbon (carbon-12).

• Carbon-14 decays into nitrogen.

Alpha Decay

• Alpha decay is the ejection of alpha particles from a nucleus.

• An alpha particle consists of two protons and two neutrons.

• Alpha decay results in a decrease in atomic number (due to the loss of protons) and mass number (due to the loss of protons and neutrons).

Beta Decay

• Beta decay is the ejection of beta particles from a nucleus.

• A beta particle is essentially the same as an electron.

• The beta particle ejected during beta decay is not one of the electrons orbiting the nucleus; instead, it forms when a neutron is converted into a proton and an electron.

• In beta decay, the atom gains a proton, thus increasing its atomic number.

Gamma Decay

• Gamma decay is the emission of gamma rays from a nucleus.

• Gamma rays are not particles but a type of electromagnetic wave, similar to X-rays but with more energy.

• Since gamma decay does not change the number of protons or neutrons in a nucleus, the atomic number and mass number remain the same.

Types of Radiation - Summary

1. Alpha ($\alpha$)

   • An atom decays into a new atom and emits an alpha particle.

   • An alpha particle consists of 2 protons and 2 neutrons (the nucleus of a helium atom).

2. Beta ($\beta$)

   • An atom decays into a new atom by changing a neutron into a proton and an electron.

   • The fast-moving, high-energy electron is called a beta particle.

3. Gamma

   • After alpha or beta decay, surplus energy is sometimes emitted as gamma radiation.

   • Gamma radiation has a very high frequency and short wavelength.

   • The atom itself is not changed during gamma decay.

*Diagram showing Unstable nucleus decaying into new nucleus by emitting:
* Alpha particle
* Beta particle
* Gamma radiation

How Radiation Affects Us

• As radiation moves through substances, it is absorbed, causing its intensity to decrease with distance.

• The three types of radiation penetrate materials to different extents.

  • Alpha radiation is the least penetrating, traveling only a few centimeters in air and being stopped by a sheet of paper.

  • Beta radiation can travel a few meters in air and can be stopped by a sheet of aluminum foil.

  • Gamma radiation is the most penetrating, traveling several hundred meters in air and requiring several centimeters of lead or a thick wall of concrete to be stopped.

• All types of radiation are damaging to living things.

  • Beta and gamma radiation can cause severe burns, sickness, and mutation.

  • Alpha radiation is relatively safe unless inhaled or ingested, at which point it becomes a serious health hazard.

Penetration Diagram

• Alpha radiation is stopped by Paper.

• Beta radiation is stopped by Aluminium.

• Gamma radiation is stopped by Lead.