P7 Flashcards
Which three main people discovered that atoms certain objects emit radiation ?
Henri bequerel , marie curie and her husband pierre
Who carried out tests to see what stopped radiation ?
Ernest Rutherford
How did Ernest Rutherford test what stopped radiation ?
He put different materials between the radioactive substance and a detector
What two types pf radiation did Ernest rutherford discover ?
Alpha and beta particles
What was the third radioactive particle that was discovered by scientists ?
Gamma radiation
Why are substances radioactive ?
The atoms of radioactive substances each have a nucleus that is unstable .
How does an unstable nucleas become stable ?
By emitting alpha , beta or gamma radiation
When an unstable nucleas emits radiation , what is this described as ?
Decaying
How can a nucleus be unstable ?
For example carbon -14 is an isotope of carbon which is unstable . It has two extra neutrons compared to the stable carbon 12.
What two things can radiation be in the form of ?
A high energy particle or a wave
The process of emitting radiation is called what ?
Radioactive decay
What is a common way of detecting radiation ?
The Geiger-Muller Tube is connected to a Geiger counter . This is a common way of detecting radiation and measuring a count rate .
What was the first observation made from Rutherfords gold foil experiment ?
Most alpha particles travel through the foil undeflected
What was the second observation made from Rutherford’s gold foil experiment ?
Some alpha particles are deflected at angles .
What did the first observation of the gold foil experiment mean ?
That there is space between the atom
What did observation 2 mean in the gold foil experiment ?
This must of meant that there are positive sub atomic particles within the atom . A proton in the middle that deflected the alpha particles .
What was observation 3 in the gold foil experiment ?
Occasionally , an alpha particle travel back from the foil
What does observation 3 mean in the gold foil experiment ?
This meant that it hit something dense in the nucleas
What did Rutherfords gold foil experiment show ?
That there was a small positively charged central nucleus where most of the atoms mass is located .
What is the symbol for alpha particles ?
A
What is an alpha particle the same as and why ?
The same as helium nucleus , this is because they consist of two neutrons and two protons.
What charge does an alpha particle have ?
They have a charge of +2
What is an alpha particle stopped by ?
Paper
What is the symbol for a beta particle ?
B
What is a beta particle ?
A fast moving electron
What charge does a beta particle have ?
-1
What is a beta particle stopped by ?
Aluminium
What is the symbol for a gamma ray ?
Y
What is a gamma ray ?
An electromagnetic wave
What charge does a gamma ray have ?
It has no charge
What is a gamma ray stopped by ?
A few mm of lead
What happens when an atom is ionised ?
The number of electrons it has changes
When an unstable nucleus emits an alpha particle what happens to its atomic and mass number ?
Its atomic number goes down by 2 and its mass number goes down by 4 . The mass and charge of the nucleus are both reduced .
Is radioactive decay a random process ?
Yes
What is a half life ?
The time it takes for the number of nuclei of a sample of radioactive isotopes to decrease by half
Give an example of a half life .
Uranium-235 has a half life of 704 million years . This means it would take 704 million years for the activity of a uranium-235 sample to decrease to half its original amount .
How do you calculate half life ?
- Measure the initial activity of the sample
- Determine the half life of this original activity.
- Measure how the activity changes with time
What is an alpha particles range in air ?
5 cm
What is a beta particles range in air ?
1 metre
What is a gamma particles range in air?
Unlimited
What is the range in air ?
Distance before they collide with air particles .
What is the ionising ability from strongest to weakest in terms of alpha , beta and gamma radiation ?
- Alpha
- Beta
- Gamma
What is ionisation ?
The ability for nuclear radiation to remove electrons from atoms to form ions .
What is the activity of a radioactive source ?
The number of unstable nuclei that decay every second .
What is contamination defined as ?
The unwanted presence of materials containing radioactive atoms on other materials .
What is irradiation ?
The process of exposing a material to alpha, beta or gamma radiation
How can we protect our selves from radiation ?
Radiation suit and lead clothing
