P7 Radioactivity Flashcards
Who discovered radioactivity?
Henri Becquerel in 1896.
He discovered it by observing an image on photographic film caused by uranium salts.
What are the three main types of radiation emitted by radioactive substances?
- Alpha (α)
- Beta (β)
- Gamma (γ)
These types differ in their properties and penetrating abilities.
What is a Geiger counter used for?
To detect radioactivity.
It consists of a Geiger-Müller tube connected to an electronic counter.
What type of radiation is stopped by paper?
Alpha radiation (α).
Alpha particles are positively charged and relatively large.
What type of radiation can pass through paper?
Beta radiation (β).
Beta particles are smaller and more penetrating than alpha particles.
Which type of radiation is the most penetrating?
Gamma radiation (γ).
Gamma rays can pass through most materials and require dense substances for shielding.
What happens to an unstable nucleus during radioactive decay?
It emits radiation and becomes more stable.
This process is random and cannot be predicted.
What did Ernest Rutherford discover about the atom’s structure?
The atom has a positively charged nucleus containing protons and neutrons.
This was demonstrated through his experiments with alpha particles and thin metal foil.
True or False: Radioactive decay can be influenced or predicted.
False.
Radioactive decay is a random event.
What is meant by the term ‘decaying’ in the context of radioactivity?
When an unstable nucleus emits radiation.
Decay results in the nucleus becoming more stable.
What is the significance of the Geiger counter clicking rapidly?
It indicates that the substance nearby is highly radioactive.
The frequency of clicks correlates with the level of radiation detected.
Why do some radioactive substances emit radiation all the time?
Their nuclei are unstable and decay continuously.
This results in a constant emission of radiation until the nucleus stabilizes.
what is a radioactive substance
A radioactive substance contains an unstable nuclei that becomes stable by emitting radiation
what are the types of radiation given out from a radioactive substance
alpha, beta, gamma
what is it called when a radioactive source emits radiation
radioactive decay
Why was the plum pudding model of the atom rejected.
Because it couldn’t explain why some alpha particles were scarred through large angles.
what conclusions were made about the atom from experimental evidence
that an atom has a small, positive,y charged nucleus where most of the atom’s mass is located.
why was the nuclear model accepted
the nuclear model explained why some alpha particles scattered through large angles
what is an isotope
an element with the same number of protons but different number of neutrons
how does the nucleus of an atom change when it emits an alpha particle
when an unstable nucleus emits an alpha particle, its atomic number goes does by 2
its mass number goes down by 4
The mass and charge of nucleus are both reduced
how does the nucleus of an atom change when. It emits a beta particle
- the atomic number of the nucleus goes up by one
- Its mass number is unchanged (because a neutron changes into a proton)
-change of the nucleus is increases and the mass of the nucleus is unchanged.
how do you represent the emission of an alpha particle from a nucleus.
represented by a helium nucleus which has 2 protons and 2 neutrons
add 2 to the atomic number
add 4 to the mass number
how to represent the emmision of a beta particle from a nucleus
add 1 to the atomic number/represented as a electron
how far can alpha radiation travel, what absorbs it and what’s the ionising power of it?
-alpha radiation has a race of a few centimetres in the air and is stopped by paper.
-It consists of particles, each composed of two protons and two neutrons
-It has the greatest ionising power.
how far can beta radiation travel, what absorbs it and what’s its ionising power?
- beta radiation has a range of about 1 metre in the air
- its stopped by a thin sheet of metal.
- it’s less ionising than alpha radiation and more ionising than gamma radiation.
- consists of fast-moving electrons emitted from the nucleus .
how far can gamma radiation travel, what absorbs it and what’s its ionising power.
- gamma radiation is stopped by thick lead
- it had an unlimited range in air
- it has lowest ionising power
- it consists of electromagnetic radiation
why are alpha, beta and gamma radiation dangerous.
alpha beta and gamma radiation ionise substances as they pass through . Ionisation in a living cell can damage or kill the cell.
What is meant by the half-life of a radioactive source?
- the average time it takes for the number of nuclei of the isotope in a sample to halve.
- for the count rate from the isotope in a sample to fall to half its initial value.
what is meant by the count rate from a radioactive source?
the count rate of a Geiger counter caused by a radioactive source decreases as the activity of the source decreases.
what happens to the count rate and the number of atoms from a radioactive isotope as it decays
the number of atoms of a radioactive isotope and the count rate both decreases by half every half life.
how do you calculate count rates after a given number of half lives?
The count rate after x amount of lives = the initial count rate / 2^x
what are radioactive isotopes are used for in medicine
radioactive isotopes are used for :
- medical imaging
- Treatments if cancer
- Tracers to monitor organs
how to choose a radioactive isotope for a particular job
how useful a radioactive isotope is depends on:
-it’s half-life
-the type of radiation it gives out.
what kind of half life should radiation have for medical imaging/tracing
For medical imaging with a radioactive isotope and for medical traces, the half-life shouldn’t be too long or too short.
How do you use radioactivity to destroy cancer cells?
A gamma beam or a radioactive implant can destroy cancer cells in a tumor.
