AQA Trilogy Physics Atomic Structure
Atom
Contains a positively charged nucleus made of protons and neutrons, surrounded by negatively charged electrons
Size of atom
Very small with a radius of 0.000000001m
Charge of proton
+1
Relative mass of proton
1
Charge of electron
-1
Relative mass of electron
1/5000 (negligible)
Charge of neutron
Relative mass of neutron
1
Charge of an atom
No charge, as atoms have the same number of protons and electrons
Size of nucleus
1/1000 of the size of the atom
Electrons move further from the nucleus
When electromagnetic radiation is absorbed by the atom
Electrons move closer to the nucleus
When electromagnetic radiation is emitted by the atom
Positive ion
When an atom loses an electron
Negative ion
When an atom gains an electron
Isotope
Atoms of the same element with the same number of protons, but different number of neutrons
Atomic number
Number of protons in the nucleus of an atom
Mass number
The sum of the number of protons and neutrons in the nucleus of an atomo
Radioactive Decay
When an unstable nucleus releases radiation in order to become more stable
Nature of radioactive decay
Random process that is impossible to predict
The activity of radioactive decay
Measured in Becquerels and is the rate at which an atom decays
Geiger-Muller tube
Equipment used to measure the activity of a radioactive source
Components of alpha radiation
Same as a helium nucleus (2 protons and 2 neutrons)
Components of beta radiation
High-speed electron as a neutron turns into a proton
Components of gamma radiation
Electromagnetic radiation (wave)
Components of neutron decay
A neutron
Ionising power of alpha radiation
Strong
Ionising power of beta radiation
Medium (reasonable)
Ionising power of gamma radiation
Poor (weak)
Paper
Alpha particles are stopped by this
Thin sheet of aluminium
Alpha and beta particles are stopped by this
Thick lead
Alpha, beta and gamma radiation is stopped by this
Contamination
Unwanted presence of materials containing radioactive atoms on other materials
Irradiation
Exposing an object to nuclear radiation. The object does not become radioactive
Half life
Time taken for half a radioactive isotope to decay or time taken for count rate to half