CP6 Radioactivity Flashcards
Explain why radiation can be damaging to humans
It is ionsing and can cause cancer
What 2 pieces of equipment are used to measure and detect radioactivity?
Geiger counter and photographic film
List ALL 6 sources of ionising radiation that you know
UV, X-ray, gamma, alpha, beta +, beta -,
What is backround radiation?
The radiation that is always present in the world
What causes there to be radiation in the world? (source of the backround radiation)
Humans setting off nuclear bombs, nuclear power stations melting down, nuclear waste, naturally occuring radioactive elements in the earth’s crust, radiation from space.
What are the similarities and differences between isotopes?
Same number of protons but a different number of neutrons.
What is the isotope notation for alpha, beta - beta +?
What is the activity of a radioactive source?
The number of counts of radiation per second
What is the S.I. unit for activity?
becquerel, Bq
What safety precautions should someone who works with radioactivity undertake?
Keep a safe disstance, point source away from people, handle source with tongs, limit exposure time, use sheilding, use gloves, use mask, wear a film badge
What equipment is used to measure radioactivity
Geiger counter
Why does data in radioactivity experiments tend to be quite scattered?
Because radioactivity is a random process so there is variation in each reading
What is the half-life of a radioactive compound? (2 definitions)
It is the time it takes for the count rate to half / the time it takes for half the nuclei to decay
How do you find half-life from a graph?
Go down to half the value on the y axis and draw a line across to the curve. Draw a line down from there to the x-axis and read of the value of time that happened at.
State the three subatomic particles
Protons, neutrons, electrons
State the masses of the subatomic particles
Protons: 1, neutrons: 1, electrons: 0
State the relative charges of the subatomic particles
Protons: +1, neutrons: 0, electrons: -1
Why do atoms have no overall charge?
Because they have the same number of electrons as protons so the charges cancels each other out.
What is the typical size of atoms or small molecules?
10^-10 m
how small is the nucleus compared to the atom?
10 000 times smaller
What happens to the electrons in an atoms when it absorbed electromagnetic radiation?
It moves to an orbit further from the nucleus
What happens to the electrons in an atoms when it emits electromagnetic radiation?
the electron move to an orbit closer to the nucleus
What is ionisation?
When at atom becomes an ion by losing electrons
What is an alpha particle?
2 protons and 2 neutrons (a helium nucleus)
what is a beta particle?
an electron emitted from the nucleus
what is a gamma ray?
an electromagnetic wave
List alpha, beta and gamma from most to least penetrating
Gamma, beta, alpha
List alpha, beta and gamma from most to least ionising
Gamma, beta, alpha
Describe the process of beta - decay
a neutron becomes a proton plus an electron which is emitted
Describe the process of beta + decay
a proton becaomes a neutron plus a positron which is emitted
Gamma radiation often occurs after another type of radiation. What is happening to the nucleus here?
The nucleus is rearranging
What is the difference between contamination and irradiation?
In contamination a source of radiation has been eaten or touched which will continue to emit radiation and cause more damage. In irradiation radiation has hit and been absorbed causing damage but no further damage will be caused.
What is the plum pudding model?
Atoms are spheres of positive charge with tiny negative electrons stuck in them
Describe Rutherford’s alpha particle scattering experiment
They fired a beam of alpha particles at a thin gold foil
What were the results of Rutherford’s alpha particle experiment?
Most of the alpha particles passed straight through, some were deflected by large amounts and some were deflected backwards
How did Rutherford’s alpha particle scattering experiment lead to the Bohr model of the atom?
In order for alpha partciles to be deflected backwards they must be hitting a very dense thing - the nucleus which contains most of the mass of the atom, for most alpha particles to pass through there must be lots of empty space. For alpha particles to be deflected they must be repelling the alpha particles and so the nucleus must be postively charged.
