P1: Atomic Structure Flashcards
What is an Alpha particle? (Not atomic structure)
A helium nucleus
What is a beta particle? (Not atomic structure)
One fast-moving electron.
What is a gamma particle? (Not atomic structure)
A high energy electromagnetic wave.
What is the atomic structure of an alpha particle?
4
2
What is the atomic structure of a beta particle?
0
-1
What is the atomic structure of a gamma ray?
0
0
What is the name of the first ever model of the atom?
The plum pudding model.
Describe the structure of the plum pudding model.
A sphere of positive charge with negatively charged electrons scattered around the atom.
Why did the plum pudding model need to change?
Ernest Rutherford discovered the nucleus with his gold scattering experiment
What were the results of the gold scattering experiment?
Most of the alpha particles passed straight through the foil,
A small number were deflected by large angles as they passed through the foil,
A very small number came straight back off the foil.
What was the gold scattering experiment?
A beam of alpha particles was directed at a very thin gold leaf suspended in a vacuum to determine the movement of particles and to test the plum pudding model of the atom
What conclusion did Rutherford come to thanks to the gold scattering experiment?
-The atom is mostly empty space.
-Like charges repel.
-Discovery of the nucleus, the positive charge and mass are concentrated in a tiny volume in the atom.
What is the name of Ernest Rutherford’s model of the atom?
The nuclear model.
Why did the nuclear model of the atom have to change?
Niels Bohr discovered energy levels in the atom that the electrons orbited in.
What is the name of Niels Bohr’s atom model?
Bohr model
Why did the Bohr model of the atom have to change?
James Chadwick proved the existence of the neutron.
How did Chadwick prove the existence of the neutron?
Performed a version of Rutherford’s gold scattering experiment, using a sheet of beryllium and a paraffin block instead of gold foil.
What is the atomic number?
The number of protons
What is the mass number?
The number of protons and neutrons
What defines an element?
Its atomic number.
What are isotopes?
Forms of an element that have the same number of protons but different numbers of neutrons.
What is an ion?
A charged particle. An atom with a different number of electrons.
How can an atom’s nucleus be stable?
If it has a certain amount of neutrons for the amount of protons it has.
What is the ionising power of alpha radiation?
High
What is the ionising power of beta radiation?
Low
What is the ionising power of gamma radiation?
Very low.
What is alpha radiation’s range in air?
Less than 5cm
What is beta radiation’s range in air?
Around 1 metre
What is gamma radiation’s range in air?
Almost infinite
What stops alpha radiation?
Skin or paper
What stops beta radiation?
3mm of aluminium foil
What stops gamma radiation?
Few cm of lead or few m of concrete.
What can radioactive activity be detected by?
A Geiger counter.
What type of process is radioactive decay?
A random process.
What is half-life?
The time it takes for half of the unstable nuclei in a sample to decay or for the activity of the sample to halve or for the count rate to halve.
What is count-rate?
Count-rate is the number of decays recorded each second by a detector, such as the Geiger counter
What is irradiation?
Exposing objects to beams of radiation.
What does irradiation from radioactive decay do?
Damages living cells.
What are the uses of irradiation?
Preserving fruit sold in supermarkets, sterilising surgical instruments, killing cancerous tumours
What is considered when applying radioactive sources in medicine?
The nature of decay, the half-life and toxicity.
What are the advantages of irradiation?
Sterilisation can be done without high temperatures
It can be used to kill bacteria on things that would melt
What are the disadvantages of irradiation?
It may not kill all bacteria on an object
It can be very harmful, leading to damage of cells and mutation
What is contamination?
When an object has radioactive material introduced into it.
What can radioactive contamination be used for?
Injecting radioactive sources to be used as tracers, can indicate bloackages
In medical applications of radioactive contamination, what types of isotopes are chosen?
Non-poisonous isotopes with very short half-lives.
What are the advantages of contamination?
Radioactive isotopes can be used as medical and industrial tracers,
Use of isotopes with a short half-life means exposure can be limited
Imaging processes can replace some invasive surgical procedures
What are the disadvantages of contamination?
Radioactive isotopes may not go where they are wanted,
It can be difficult to ensure that the contamination is fully removed,
Exposure to radioactive materials can potentially damage healthy cells.
What is the difference between irradiation and contamination?
Irradiation occurs when an object is exposed to a source of radiation outside the object,
Contamination occurs if the radioactive source is on or in the object.
What are the effects of radiation on the eyes?
High doses can cause cataracts.
What are the effects of radiation in the stomach?
Radioactive isotopes can sit in the stomach and irradiate for a long time
What are the effects of radiation on reproductive organs?
High doses can cause sterility or mutations.
What are the effects of radiation on skin?
Radiation can burn skin or cause cancer.
What are the effects of radiation on bone marrow?
Radiation can cause leukaemia and other diseases of the blood.
What is the simplest measure of radioactivity?
The Becquerel (Bq).
Give some examples of background radiation.
Cosmic rays, radon gas from the ground, medical, nuclear power and weapons testing, food and drink,
What is the unit to measure radiation dose?
Sievert (Sv).
What is nuclear fission?
The splitting of a large atomic nucleus into smaller nuclei.
A neutron is absorbed into a nucleus, which makes the nucleus violently unstable and splits the nucleus into daughter nuclei and some extra neutrons.
These neutrons react with the daughter nuclei and the process repeats.
What is nuclear fission used for?
Heats water to drive turbines that turn generators
What is nuclear fusion?
When two small, light nuclei join together to make one heavy nucleus.
Some mass is missing, which is converted to energy which radiates away.
What is the problem with nuclear fusion?
Is requires the fusing of nuclei, which are positive particles (so they repel). The only way to get fusion to occur is to make the nuclei move rapidly, which can only be done by placing them in extremely high temperatures.
What happens if the chain reaction in nuclear fission is not controlled?
The speed of the chain reaction increases very quickly, producing a huge amount of energy very quickly, which can lead to explosions.
How are nuclear fission chain reactions controlled in a nuclear power station?
Control rods are lowered into the nuclear reaction to absorb neutrons to prevent the chain from absorbing them instead, slowing the chain reaction.
Why are some isotopes radioactive?
Because they are unstable.
Where does a beta come from?
A neutron in a nucleus becomes a proton, and an electron is ejected.
What are the four types of radioactive emissions?
Alpha, beta, gamma, neutron.
