Radioactivity Flashcards
(17 cards)
What is meant by the term half life?
The time taken for the activity of the radioactive sample to half.
Why does the activity of a radioactive sample reduce with time?
The radioactive sample is unstable meaning it has too many neutrons so it loses one to make it more stable.
Nucleus decays and fewer nuclei are left after some time.
Describe the structure of an atom
Atoms are made up of smaller particles called neutrons, protons, electrons. Neutrons and protons are in the nucleus and electrons in the outer shell.
What is meant by the ionisation of an atom?
The process by which an atom becomes negatively or positively charged by gaining or losing electrons
What is meant by ionising radiation?
The radiation emitted from unstable nuclei is called ionising radiation because as it passes through matter it can dislodge outer electrons from atoms causing them to become ions.
What are the three types of ionising radiation given of by the nuclei of atoms?
Alpha particle, beta particle and gamma rays
What is meant by a radioactive substance?
A substance containing unstable atoms
What is an isotope?
with the same number of protons but different numbers of neutrons
What is radioactive decay?
The emission of energy in the form of ionising radiation
What is an alpha particle?
Composite Particles consisting of two neutrons and two protons
What is a beta particle?
An electron ejected from a nucleus when a neutron becomes a proton
What is gamma radiation?
High energy electromagnetic waves emitted from unstable nuclei
What is the activity of a radioactive source?
The rate at which the isotope decays
What is meant by the random nature of the radioactive substance?
Is it is possible to predict when a particular radioactive nucleus will decay
What is meant by the spontaneous nature of radioactive decay?
You cannot cause or influence the decay to happen
How much of a radioisotope remains after 2 half lives?
50%
How much of a radioisotope remains after 1 half life?
25%
