Lesson 6: Nuclear Reactions

Types of Decay

Decay is the process where a nucleus undergoes a reaction and emits radiation.

Alpha Decay - loss of an Alpha particle

Beta Decay - loss of a Beta particle

Gamma Decay - loss of a Gamma particle 

Alpha Decay and particle

When a nucleus is very heavy (greater than 150 mass units) it expells an alpha particle.

An alpha particle contains 2 protons and 2 neutrons and looks a lot like a helium nucleus.

This particle is +2 in charge and moves at 10% of the speed of light.
It is unable to pass trhough paper or anything thicker and is very ionising (radioactive).

Beta Decay and particle

When a nucleus contains too many neutrons, one necutron can be converted to a proton expelling a beta particle.

An beta particle 1 electron.

This particle is -1 in charge and moves at 90% of the speed of light.
It is unable to pass through aluminium or anything thicker and is relatively ionising (radioactive).

Gamma Decay and particle

Sometimes particles in the nucleus rearrange spontaneously, they can produce a gamma ray.

A gamma ray is a form of electromagnetic light siliare to X-rays but far more powerful.

This particle is neutral in charge and moves at the speed of light.
It is able to pass through everything but lead or water and is not very ionising (radioactive).

Half-life

A half-life is a the time it takes for half of a sample of radioisotopes to decay.

After 1 half-life 50% of the isotopes will decay leaving 50% of the original.
After 2 half-lives 75% of the isotopes will decay leaving 25% of the original. 

After 3 half-lives 87.5% of the isotopes will decay leaving 12.5% of the original. 

After 4 half-lives 93.75% of the isotopes will decay leaving 6.25% of the original.