Radioactive decay Flashcards
What is the basic structure of an atom?
A small central nucleus composed of protons and neutrons surrounded by electrons.
What is the relative mass of a neutron?
1.
What is the relative mass of a proton?
1.
What is the relative mass of an electron?
Very small (1/2000).
What is the relative charge of a neutron?
0.
What is the relative charge of a proton?
+1.
What is the relative charge of an electron?
-1.
In an atom the number of electrons is equal to…
…the number of protons in the nucleus.
What can be said about the overall electrical charge in and atom?
There is no overall charge because the number of protons is equal to the number of electrons.
When an atom gains or loses electrons it becomes a what?
An ion.
Atoms of an element always have the same number of protons, but what is an atom of an element if it has a different number of neutrons?
An isotope of that element.
The total number of protons in an atom is known as what?
The atomic number.
The total number of protons and neutrons in an atom is known as what?
The mass number.
A substance is referred to as radioactive if it does what?
Gives out radiation all the time from the nuclei of its atoms no matter what is done to it.
True or false, radioactive decay is systematic?
False, radioactive decay is a random process.
What are the origins of background radiation?
The rocks we live above. Radiation from space. Building materials. Nuclear accidents. Nuclear weapons testing.
What is an alpha particle?
A particle with only two neutrons and two protons (the same as a helium nucleus).
What is a beta particle?
An electron from the nucleus.
What is gamma radiation?
Electromagnetic radiation in the form of gamma rays.
Properties of alpha particles?
1/3 speed of light, weakly effected by magnetic field, strongly ionising, +2 charge, travels short distance in air and won’t penetrate skin/paper.
Properties of beta particles?
2/3 speed of light, strongly effected by magnetic field, weakly ionising, -1 charge, penetrates skin/paper but absorbed by aluminium.
Properties of gamma rays?
Speed of light, no magnetic effect, very weakly ionising, 0 charge or mass, stopped by thick lead or concrete.
What is meant by the term ionising?
The radiation can break molecules into ions.
What types of radiation can be deflected by a magnetic field?
Alpha and beta radiation can be deflected, however a magnetic field has no effect on gamma radiation.
Alpha radiation can be used how?
Used in smoke alarms. When smoke moves between the source and detector the radiation is absorbed and the alarm sounds.
How can beta radiation be used?
In paper mills. If the paper is thicker between the source and detector more radiation is absorbed so the rollers are narrowed and the paper is made thinner. If the paper is thin less radiation is absorbed so the rollers are widened to make the paper thicker.
Uses of gamma radiation?
Sterilisation of food and medical equipment.
Radiotherapy.
Leaking pipes (put source in pipe with short half life and detect where the leak is).
What is the half life of a radioactive isotope?
The average length of time it takes for the number of nuclei of an isotope in a sample to half, or the time it takes for the count rate of a sample containing the isotope to fall to half its initial level.
