Atoms + radiation Flashcards
What is the nucleus?
The centre of the atom, containing protons and neutrons.
What are electrons?
Negatively charged particles that orbit the nucleus at fixed distances.
What is the radius of atoms?
1 x 10^-10 metres
What is the mass and charge of protons?
Mass=1
Charge= +1
What is the mass and charge of neutrons?
Mass=1
Charge=0
What is the mass are charge or electrons?
Mass=1/1800
Charge=-1
What is the mass number?
Top number, protons + neutrons.
What is the atomic number?
Bottom number, protons and electrons.
What are isotopes?
An element with the same number of protons but different numbers of neutrons.
Define ionisation
The process of an atom becoming a charged particle (make an ion).
What is emission?
When an electron emits energy as it moves down an energy level.
When do atoms become charged?
When they lose or gain electrons.
When is a positive ion formed?
When an atom loses one or more electrons.
When is a negative ion formed?
When an atom gains one or more electrons.
When do electrons move up an outer shell?
When they gain energy by absorbing electromagnetic radiation.
Who created the Plum Pudding model and when?
JJ Thompson in 1897.
What did JJ Thompson discover?
The electron.
What does the Plum Pudding model look like?
A cloud of positive charge with negative electrons embedded in it.
Who created the Nuclear Model of the atom and when?
Ernest Rutherford in 1911.
What did Ernest Rutherford discover?
A small positive nucleus in the atom.
How did Rutherford discover the nucleus?
Discovered it in his alpha scattering experiment.
What does the Nuclear model of the atom look like?
Ball with electrons orbiting the nucleus but not at set distances.
What was step one of the alpha scattering experiment?
1 = Alpha particles (small, positively charged particles) fired at thin gold foil.
What was step two of the alpha scattering experiment?
2 = The scientists were expecting the alpha particles to go straight through the gold.
What was step three of the alpha scattering experiment?
3 = The scientists were surprised that a small number of alpha particles bounced back and some were deflected.
What was step four of the alpha scattering experiment?
4 = Scientists suggested that the positive charge and mass of an atom must be concentrated in a small space in the centre and named the space the nucleus. They also said that because some passed through the atom was mainly empty space.
What was Niels Bohr’s version of the atom?
The shell model created in 1913
What did Bohr discover?
The electrons exist in shells.
What did James Chadwick discover in 1932?
The neutron.
Where is the majority of an atom’s mass?
The nucleus.
What is radioactive decay?
When an unstable nucleus becomes more stable over time by emitting nuclear radiation and the process is random.
Which type of radiation is most penetrating?
Gamma.
Which type of radiation is least penetrating?
Alpha.
What is alpha radiation used in?
Smoke detectors.
What is gamma radiation used in?
- Sterilisation of medical equipment.
- Patient blood flow.
What is beta radiation used for?
Paper production.
What happens in the nucleus in an alpha particle?
The nucleus loses 2 protons and 2 electrons.
What happens in the nucleus in a beta particle?
A neutron changes into a proton and an electron.
What happens in the nucleus in a gamma particle?
Some energy is transferred away from the nucleus.
What is the ionising power of an alpha particle?
Highest ionising power.
What is the ionising power of a beta particle?
High ionising power.
What is the ionising power of a gamma particle?
Low ionising power.
What is an alpha particles range in air?
Travels a few cm in air.
What is a beta particles range in air?
Travels 1m in air.
What is gamma’s radiation in air?
Virtually unlimited range in air.
What stops alpha particles?
A sheet of paper.
What stops beta particles?
A few mm of aluminium.
What stops gamma radiation?
Several cm of thick lead or m of concrete.
What is half life?
The time it takes for either:
-Half of the radioactive nuclei in a sample to drop 50% of the original number.
OR
-The activity of a sample to drop by 1/2.
What is the other name for the atomic number on the periodic table?
Z.
What is the other name for the mass number on the periodic table?
A.
What is contamination?
When radioactive atoms get onto other materials.
What is irradiation?
When an object is exposed to nuclear radiation.
Why is tinned food irradiated?
To lengthen its shelf life.
How can we reduce irradiation?
Standing behind lead or storing radioactive material in lead-lined boxes.
What can ionising radiation do?
Damage cells, cause mutations that lead to cancer and possibly organ failure.
How should we store radioactive materials?
In lead-lined boxes and locked in steel cabinets.
What should we do when storing radioactive materials?
- Not handled directly.
- Short time.
- Use rubber gloves.
- Wash hands thoroughly after use.
What is the most dangerous form of radiation for the body?
Alpha as it cannot penetrate the skin so stays in the body, causing cell mutations.
