P6 - Radioactive Materials Flashcards
Rutherford-Geiger-Marsden experiment results…
- Was done to find results supporting the plum pudding model of the atom
- Results were unexpected: scientists expected all alpha particles to go through the thin foil but some emerged at different angles and some were deflected back
- 1905
Rutherford-Geiger-Marsden experiment conclusions…
- Positively charged alpha particles were being repeller by a tiny concentration of positive charge in the foil atoms
- The plum pudding model was replaced with the nuclear model
- most of the space taken up by atoms must be empty
- the majority of the mass is in the nucleus
Protons and neutrons are held together in the nucleus by…
A strong force which balances the repulsive electrostatic force between the protons
Nuclear fusion is..
When hydrogen nuclei are brought close enough together they have the ability to fuse and create helium nuclei and release energy
E=mc^2 is used to calculate…
Energy released during nuclear fission and fusion
An isotope is…
A form of an element with a different number of neutrons (every atom of an element has the same number of protons)
The behaviour of radioactive materials…
Cannot be changed by chemical or physical process
The three types of ionising radiation are…
Alpha, beta and gamma
Alpha particles are…
2 protons and 2 neutrons, identical to helium nuclei
Beta particles are…
A high speed electron
Alpha radiation is…
Highly ionising and weakly penetrating, it can be stopped by a piece of paper.
Beta radiation is…
Moderately ionising and moderately penetrating, it can be stopped by a thin piece of aluminium.
Gamma radiation is…
Weakly ionising and highly penetrating, high levels can be stopped only by many cm of lead of many metres of concrete
Over time the radioactivity of a source _____
Decreases
Half life is…
- The time it takes for a number of atoms in a sample to halve
- The time it takes for the activity of a source of radiation to fall by half
