Chapter 6 - Radioactivity Flashcards
What are the three types of radiation emitted
- Alpha radiation
- Beta radiation
- Gamma radiation
Can you tell when an unstable nucleus will decay?
You cannot predict when an unstable nucleus will decay. It is a random process and is not affected by external conditions
What is background radiation
Radiation from radioactive substances in the environment, from space, from devices such as x-Ray tubes
What was the alpha particle scattering experiment
Where alpha particles were fired at thin gold foil
Why did most of the atom particles pass through through the foil
Because most of the atom is just empty space
Why did some of the alpha particles become deflected through small angles
Because the nucleus has a positive charge so some of the alpha particles rebound as they must be repelled by another positive charge
Why would a few alpha particles rebound through very large angles
If the nucleus has a large mass and a very large positive charge
What happens in alpha decay
The nucleus loses 2 protons and 2 neutrons and are emitted as an alpha particle
What happens in beta decay
A neutron in the nucleus changed into a proton and electron and the electron created is instantly emitted
What are the issues with ionisation
It kills or damages living cells
What is half life used for
To measure how quickly the radioactivity decreases.
How do the nuclei of radioactive substances become stable
By radioactive decay. In this process they emit radiation and turn into other elements
What is an isotope
Atoms of same element with different numbers of neutrons
What does an alpha particle consist of
2 protons and 2 neutrons. It has a relative mass of 4 and its relative charge is 2+
It is represented as 4 a
2
What is a beta particle and what does it consist of
A high speed electron from the nucleus, emitted when a neutron in the nucleus changes to a proton and electron. It’s relative mass is 0 and its relative charge is -1
It is represented as 0 B
-1
Does gamma ray have a charge or mass
No because a gamma ray is an electromagnetic wave released from the nucleus
Why does ionisation occur
When nuclear radiation travels through a material it will collide with the atoms of the material. This knocks electrons off them, creating ions.
How ionising are alpha particles
Strongly ionising because they are relatively large so they have lots of collisions - because of these collisions they do no not penetrate far into the material
How can alpha particles be stopped
By a thin sheet of paper, human skin or few centimetres of air
How ionising are beta particles
Less ionising than alpha particles as they are much smaller and faster. They can penetrate further
How are beta particles blocked
By a few metres of air of thin sheet of aluminium
How ionising are gamma rays
Weakly ionising but very penetrating. Not deflected by electric and magnetic fields like alpha particles and beta particles
Where are alpha sources used
In smoke alarms
What are beta sources used for
Thickness monitoring in manufacturing things like paper or metal foil.
What are gamma and beta sources used as
As tracers in medicine. Source is injected or swallowed be patient. Progress around body monitored by detector outside patient
What is radioactive dating used for
To find the age of ancient material.
