2- Radioactivity Flashcards
What is radioactive decay?
When an unstable nucleus randomly emits radiation and turns into other elements - becoming stable
Give examples of where background radiation comes from?
Space and devices such as X-ray tubes
What did scientists used to think about atoms before nucleus’s were discovered?
The ‘plum pudding’ model
Atoms were spheres of positive charge with electrons stuck into them
How did Rutherford, Geiger and Marsden discover the nucleus?
With an alpha particle scattering experiment - firing alpha particles at thin gold foil.
Alpha particles being deflected (at large angles) meant the nucleus had a large mass and positive charge.
What happens during alpha decay in nuclear reactions?
The nucleus loses 2 protons and 2 neutrons which are emitted as alpha particles
What happens during beta decay in nuclear reactions?
A neutron in the nucleus changes into a proton and an electron, where the electron is instantly emitted
What is 1)the atomic number 2)the mass number
1) The bottom number which is the number of protons (normally the number of electrons)
2) the top number which is the number of protons plus neutrons
(To find the no. of neutrons u minus the big no. from the small
What is an alpha particle?
Consisting of two protons and two neutrons, it has a relative mass of 4 and a charge of +2
What is a Beta particle?
A high speed electron from the nucleus emitted when a neutron changes into a proton and an electron (beta decay)
It’s relative mass is 0 and it’s charge is -1
What is a gamma ray?
Not altering the number of neutrons or protons, a gamma ray is an electromagnetic wave released form the nucleus
No charge or mass
What happens when nuclear radiation travels through a material?
It will collide with the atoms of the material, knocking electrons off them (creating ions) - ionisation which can damage or kill a living cell
What happens when an alpha particle travels though a material? Explain
Because they are relatively large, they have lots of collisions with atoms (strongly ionising). Because of this, alpha particles do not penetrate far - deflected by electric and magnetic fields
What can stop 1)alpha 2)beta 3)gamma particles?
1) thin sheet of paper or a few cm of air
2) thin sheet of aluminium or a few m of air
3) several cm of lead or concrete to absorb it
What are some features of beta particles?
Much smaller and faster and less ionising than alpha particles
Deflected by electric and magnetic fields in the opposite direction to alpha particles
What are some features of gamma rays?
Weak ionising
Very penetrating
Not deflected by electric and magnetic fields
