Section 19 - Radioactivity - Isotopes, nuclear radiation, half-life, background radiation and contamination Flashcards
What are isotopes?
Different forms of same element, with same number of protons but different number of neutrons
What is radioactive decay?
When unstable isotopes tend to decay into other elements and give out radiation as they try to become more stable
What type of nuclei is an alpha particle?
Helium nuclei
What is emitted in alpha decay by the nucleus? What happens to the atom?
Nucleus emits an alpha particle (2 protons, 2 neutrons) so mass number decreases by 4 and atomic number decreases by 2
What is formed and why in alpha and beta emissions?
A new element is formed as the number of protons changes
What is emitted in beta-minus decay by the nucleus? What happens to the atom?
A neutron changes into a proton and an electron as fast-moving electron is emitted so mass number doesn’t change and atomic number increases by 1
What is emitted in beta-plus decay/positron emission by the nucleus? What happens to the atom?
A proton changes into a neutron and a positron and a fast-moving positron is emitted so mass number doesn’t change and atomic number decreases by 1
What is a positron?
Antiparticle of electron. Has exact same mass as electron but positive (+1) charge
What is emitted in neutron emission by the nucleus? What happens to the atom?
A neutron is emitted so mass number decreases by 1 and atomic number stays the same
What is the penetration like, range, and ionising type in alpha particles?
Don’t penetrate very far into materials and stopped quickly due to size
Can only travel a few cm in air before absorbed
Strongly ionising due to size
Range and ionising type in both beta-minus (β-)and beta-plus (β+) particles?
Both moderately ionising
β- - has range in air of few metres and absorbed by sheet of aluminium
β+ - Smaller range due to when they hit an electron, it annihilates
What is annihilation?
When a positron hits an electron, causing the two to destroy each other and produce gamma rays
What is emitted in gamma (γ) radiation? What happens to the atom?
Gamma rays (γ) are emitted as a way of getting rid of excess energy from atom. Nucleus goes from an excited state to a more stable state. Mass and atomic numbers stay the same
What is the penetration like, range and type of ionising in gamma radiation (γ)?
Penetrate very far into materials without being stopped
Travels a long distance through air. Can be absorbed by thick sheets of lead or metres of concrete
Weakly ionising as they tend to pass through rather than collide with atoms but eventually hit something and do damage
What is activity and measured in what?
The rate at which a source decays and measured in becquerels, Bq (1 decay per sec)
