Radioactivity

Why are large nuclei more likely to be radioactive than small nuclei? protons and neutrons are held together less tightly in a large nucleus than in a small one. This makes them unstable. Radioactive elements start at atomic # 84.

What do we mean by Radioactivity? Radioactive decay is the process where an unstable nucleus loses energy by emitting radiation in the form of particles or waves. An unstable nucleus releases energy to become more stable

Three known types of radiation Alpha particles (a) Beta particles (b) Gamma-rays (g)

What stops them? Alpha particles are stopped by a sheet of paper Beta particles by aluminum sheeting. Gamma rays by thick pieces of lead.

How is radiation detected? Cloud chamber: uses condensed vapor. Bubble Chamber: bubble trail in superheated liquid. Electroscopes: measure charged particles in the air. Geiger Counter: produces an electric current when radiation is present.

Radioactivity – Is it a Health Problem? All three add energy to your body tissues. This can alter your DNA

Medical Applications of Radioactivity Radiotracers Put inside organisms and traced for diagnostic purposes. Example is Iodine-131 to test the thyroid

What is a half life? The time it takes for half of the original sample of radioactive nuclei to decay. Transmutation is the process of 1 element’s changing to another through nuclear decay.

Nuclear Fission Nuclear Fission is the splitting of a nucleus into smaller masses. Releases LOADS of energy.

This is how nuclear power plants work. A chain reaction is a series of fission reactions. Think of a chain of dominoes. Critical mass is the amount of fissionable material required to continue a reaction at a constant rate.

NUCLEAR FUSION Nuclear fusion occurs when 2 nuclei at low mass are combined, making 1 large mass. Nuclear fusion can only happen when nuclei are moving fast enough to get close to each other. Requires super high temperatures like those found in stars.