Where is most of an atom’s mass concentrated?
Nucleus
What are isotopes?
Atoms of same element with different numbers of neutrons
What happens to atoms if they lose an outer electron?
They become a positive ion
Why are some atomic nuclei unstable?
There is an imbalance in the forces acting with them, causing radioactive decay
What is radioactive decay?
Random process by which unstable atomic nuclei lose energy by emitting radiation, transforming the nuclei into a more stable form
Unit of activity?
Becquerel
What is an alpha particle?
Particle consisting of 2 neutrons and 2 protons
What is a beta particle?
High speed electron ejected from nucleus as a neutron turns into a proton
What is a gamma ray?
Electromagnetic radiation from the nucleus
Ionising power of alpha, beta, gamma
Very strong, medium, weak
Air range of alpha, beta, gamma
10 cm, 1m, infinite
Which materials can alpha, beta, gamma not penetrate through
Paper, thin aluminium, thick lead
What is the half-life of a radioactive isotope?
Average time taken for half of a radioactive sample to decay
Relation between half-life and hazard of radioactive material
Shorter half-life is high radiation intensity in a short amount of time, longer half-life is low radiation intensity across a long amount of time
What is radioactive contamination?
Unwanted presence of materials containing radioactive atoms on other materials
What is irradiation?
Process of exposing object to nuclear radiation; irradiated object doesnt become radioactive
Size of atom radius
1 times 10 to power of -10
How is nuclear radiation used to explore internal organs?
Radioactive isotope enters body and emits gamma radiation as it travels through body which is detected by gamma detector outside body; detector shows patterns that help identify problems
What was the plum pudding model?
A model that suggested atom is ball of positive charge with negative electrons embedded in it
What was Rutherford’s nuclear model?
Nucleus at centre of atom orbited by electrons
What does alpha decay do to mass and charge of nucleus?
Makes both decrease
Why results of Rutherford’s experiment disprove plum pudding model
experiment showed that most alpha particles passed straight through the foil, but some were deflected at large angles. This disagreed with Thomson’s model, which predicted only slight deflections because positive charge was spread out. The results showed that the atom has a tiny, dense, positively charged nucleus, leading to the nuclear model.
What does beta decay do to mass and charge of nucleus?
Doesn’t affect mass but increases charge
What is nuclear fission?
Splitting of large and unstable nucleus
