Radioactivity Flashcards
Nucleus
The very small and dense part of an atom, which contains protons and neutrons
Proton
A tiny positive particle found inside the nucleus of an atom
Neutron
A dense particle found in the nucleus of an atom. It is electrically neutral, carrying no charge
Electron
A tiny particle with a negative charge. Electrons orbit the nucleus in atoms or ions
Alpha radiation
Alpha particles, each composed of two protons and two neutrons, emitted by unstable nuclei
Gamma radiation
Electromagnetic radiation emitted from unstable nuclei in radioactive substances
Alpha (α) decay
The nucleus loses 2 protons and 2 neutrons, which are emitted as an α particle
Beta (ß) decay
A neutron in the nucleus changes into a proton and an electron - the electron is instantly emitted
Isotope
Isotopes of an element are atoms with the same number of protons but different numbers of neutrons. Therefore they have the same atomic number but different mass numbers
Ionisation
Any process in which atoms become charged
Tracers
A small amount of a radioactive substance used to give information about a mechanical or biological system
Radioactive dating
The use of a radioactive substance to give information about the age of an object
Carbon dating
A type of radioactive dating used to fine the age of organic materials
Uranium dating
A type of radioactive dating used to find the age of igneous rocks
What is a radioactive substance?
A radioactive substance contains unstable nuclei that become stable by emitting radiation
What types of radiation are given out from a radioactive substance?
Alpha, beta and gamma radiation
When does a radioactive source give out radiation?
Radioactive decay is a random event - we cannot predict or influence when it will happen
Where does background radiation come form?
Background radiation is from radioactive substances in the environment or from space or from devices such as X-ray machines
How was the nuclear model of the atom established?
Rutherford used the measurements from alpha-scattering experiments to prove that an atom has a small positively charged central nucleus where most of the mass of the atom is located
Why was the plum pudding model of the atom rejected?
The plum pudding model could not explain why some alpha particles were scattered through large angles
Why was the nuclear model accepted?
The nuclear model of the atom correctly explained why the alpha particles are scattered and why some are scattered through large angles
How does the nucleus of an atom change when it emits an alpha particle?
The nucleus loses 2 protons and 2 neutrons, which are emitted as an α particle
How does the nucleus of an atom change when it emits a beta particle?
A neutron in the nucleus changes into a proton, creating an electron which is instantly emitted
What are the properties of alpha radiation?
α radiation of stopped by paper, has a range of a few centimeters in air and consists of particles, each composed of two protons and two neutrons
What are the properties of beta radiation?
ß radiation is stopped by thin metal, has a range of about a metre in air and consists of fast-moving electrons emitted from the nucleus
What are the properties of gamma radiation?
Ɣ-radiation is stopped by thick lead, has an unlimited range in air and consists of electromagnetic radiation
How can we separate a beam of alpha, beta and gamma radiation?
A magnetic or electric field can be used to to separate a beam of alpha, beta and gamma radiation. α-radiation is deflected in one direction, ß-radiation in the opposite direction. Ɣ-radiation and neutrons are undeflected by the magnetic radiation
What is alpha, beta and gamma radiation dangerous?
Alpha, beta and gamma radiation ionise substances the pass through. Ionisation in a living cell can damage or kill the cell
What do we mean by the “half-life” of a radioactive source?
The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in sample to halve
What do we mean by the activity of a radioactive source?
The activity of a radioactive source is the number of nuclei that decay per second
What happens to the activity of a radioactive isotope as it decays?
The number of atoms of a radioactive isotope and the activity both decrease by half every half-life
How do we chose a radioactive isotope for a particular job?
The use we can make of a radioactive isotope depends on its half life and the type of radiation it gives out
How can we use radioactivity for monitoring?
We can use a radioactive to measure the thickness of foil by measuring the amount of radiation passing through it. The isotope should have a long half-life
What are radioactive tracers?
Radioactive tracers are used to trace the flow of a substance through a system. They should be ß or Ɣ emitters that last long enough to monitor but not long enough to cause damage to the body
What do we need for radioactive dating?
For radioactive dating of a sample, we need a radioactive isotope that is present in the sample which has a half-life about the same as the age of the sample
