P7 Radioactivity Flashcards
What can you use to detect radioactivity
A geiger-Muller tube connected to an electronic counter.
How can you tell the radiation when using a geiger muller tube
The counter clicks each time a particle of radiation from a radioactive substance enters the geiger tube.
What are the three main types of radiation
-alpha radiation
-beta radiation
-gamma radiation
What is a radioactive substance
A substance which contains an unstable nuclei that become stable by emitting radiation.
What type of event is radioactive decay
It is a random event-you can’t predict or influence when it will happen
What do radioactive sources emit
Alpha, beta and gamma radiation
What did Rutherford use the alpha particles for
To probe inside atoms. He found that some alpha particles were scattered through large angles after firing them at a thin gold foil.
What was the problem with the plum pudding model
The plum pudding model couldn’t explain why some alpha particles were scattered through large angles.
What is the structure of an atom
An atom has a small positively charged nucleus which contains protons and neutrons and is where most of the atom’s mass is located. The nucleus is orbited by electrons (negative charge) which are sorted in shells.
What is good about the nuclear model of the atom
It correctly explains why some alpha particles scattered through large angles in Rutherford’s experiment.
How does an unstable nucleus become more stable
By emitting an alpha or a beta particle or by emitting a gamma ray.
What are isotopes of an elememt
Atoms with the same number of protons but different numbers of neutrons. As a result they have the same atomic number but different mass numbers.
Changes in the nucleus after alpha decay
The nucleus loses 2 protons and 2 neutrons
Changes in the nucleus after beta decay
A neutron in the nucleus changes into a proton.
Particles emitted after alpha decay
2 protons and 2 neutrons emitted as an alpha particle
Particles emitted after beta decay
An electron is created in the nucleus and instantly emitted.
How easily is alpha radiation stopped
It is stopped easily by paper and has a range pf a few c, in air. It has the greatest ionising power.
What is beta radiation stopped by
A thin sheet of metal and has a range of about one metre in air. It is less ionising than alpha radiation and more ionising than gamma radiation.
What is gamma radiation stopped by
Thick lead and has an unlimited range in air. It consists of electromagnetic radiation
What do alpha, beta, and gamma radiation do to substances
They ionise substances they pass through. Ionisation in a living cell can damage or kill the cell.
What is the half-life of a radioactive isotope
The average time it takes for the number of nuclei of the isotope in a sample to halve.
What is the relation between the count rate of a geiger counter and the activity of the source
As the count rate of a geiger counter caused by a radioactive source decreases so does the activity of the source
What happens to the number of atoms and count rate of a radioactive isotope each half life
They both decrease by half every half-life.
