4- Atomic Structure Flashcards
What is carbon dating?
Uses the half-life of Carbon 14, to measure the age of wood, bone, paper and cloth
What is radioactive decay?
when radioactive substances are unstable, and so continuously give out radiation in random intervals.
Explain the dangers associated with radioactive sources? (6 marks)
Alpha- most ionising
Outside body, can’t pass trhough the skin
Inside body, most damage
Beta and gamma- cause damage from outside as well as inside, but less than alpha (when inside)
Long term exposure leads to damage in DNA
What is a radioisotope?
an isotope that is radioactive
isotope- atom with same number of protons, different number of neutrons
What is the activity of a radioactive substance?
the amount of radioactive decays happening per second
What is activity of a radioactive substance measured in?
Becquerels (Bq)
What is the activity of a radioactive substance measured with?
Geiger-Muller Tube
What is Half-life
the time taken for the number of nuclei in a sample to half
What is the mass and proton numbers of an alpha particle?
mass number-> 4
proton number-> 2
What is the mass and proton numbers of an beta particle?
Mass number-> 0
Proton number-> -1
What is the mass and proton numbers of an gamma particle?
Mass number-> 0
Proton number-> 0
What are radioactive traces + use?
Used to trace the flow of a substance through an organ.
Contains a radioactive isotope that emits gamma radiation –> can be detected outside the system
What can radioactive traces be used for?
This can be used to as an example find out if the kidneys are blocked
For this the patients drinks water with the substance in it and then detectors are placed over the kidneys
If the substance flows in and out of the kidneys the levels would go up and down, if the kidney’s are blocked the levels would at some point stop.
Why is radioactive iodine safe to use?
its half life is eight days –> it stays long enough for the test to be done but decays completely after a few weeks
it emits gamma so can be detected outside the body
decays into stable products
Also used in gamma cameras –> takes pictures of organs
Patient is injected with solution with gamma emitting radioactive isotope, absorbed by the organ.
What are gamma cameras?
takes pictures of organs
Patient is injected with solution with gamma emitting radioactive isotope, absorbed by organs. (works like xrays)
How is radiation used in radiotherapy?
Gamma radiation used in narrow beam used to destroy cancer tumours
Radioactive implants - beta or gamma emitting isotopes in the form of small seed or tiny rods. Permanent implants’ half life should be long enough to irradiate tumours over a given time
How do workers working with radiation protect themselves?
Workers exposed to ionising radiation must wear personalised radiation monitor, like film badge
How does nuclear fission work?
- a high energy neutron hits a nucleus (of plutonium or uranium), which splits and creates 3 high speed neutrons
- these neutrons then go off at high speeds and each hit another nucleus
- this nucleus then splits and creates 3 high speed neutrons
- this chain reaction is continued in a controlled way
What is the difference between control rods and fuel rods?
Control rods- absorb neutrons if there are too many within the fuel rods
Fuel rods- contain the nuclear fuel (contains nuclear fission reaction)
Where does nuclear fusion take place?
In the sun
hydrogen to iron in the periodic table: when they fuse in the sun, doesn’t it create or need energy?
It creates energy, past Iron, it needs energy to be fused
What happens in a fusion reactor?
the light nuclei plasma must be heated to very high temperatures and pressures
before nucleus will fuse –> nuclei will repel (positive charge) but if they move fast enough they can overcome this force
What is plasma contained by in a fusion reactor and why?
Plasma is heated by passing a very big electrical current through it
Plasma is contained by a magnetic field so that it doesn’t touch the reactor walls so that it doesn’t become cold (if it became cold,
the fusion would stop
The fuel for this is heavy hydrogen which can be found in abundance in the sea
What is the charge of an Alpha particle?
1
What is the charge of a Beta particle?
-1
What is the charge of a Gamma particle?
0
What is the mass of an Alpha particle?
1
What is the mass of a Beta particle?
0
What is the mass of a Gamma particle?
0
What is the penetration ability of an Alpha particle?
a few sheets of paper
What is the penetration ability of a Beta particle?
thin sheets of aluminium
What is the penetration ability of a Gamma particle?
thick block of lead
What is the range in air of an Alpha particle?
5cm
What is the range in air of a Beta particle?
1m
What is the range in air of a Gamma particle?
5m
What is an Alpha particle?
a helium nucleus
What is a Beta particle?
a high speed electron
What is a gamma particle?
a light ray
What is the ionising ability of an Alpha particle?
Maximum
What is the ionising ability of a Beta particle?
Medium
What is the ionising ability of a Gamma particle?
Minimum
What did JJ Thompson discover?
Electrons, and that therefore atoms are made up of smaller particles
What did Ernst Rutherford discover?
That the atom was made of a central nucleus with electrons orbiting it
What did Neils Bohr discover?
That electrons orbit at specific distances from the atom (in shells)
What is the ‘Rutherford scattering experiment’ ?
- alpha particles were launched towards a sheet of thin gold foil
- most particles passed through it, some deflected at a small angle
- very few were deflected by more than 90 degrees
- He then concluded the atom was almost entirely solid, and that there’s a positive charge at the centre of an atom, which had electrons orbiting around it
What are problems with carbon dating?
- contamination from other materials
- contamination from background radiation
How does nuclear fusion work?
Fusion is the combining of two small nuclei into one large nucleus. Only happens if there is enough energy between the two nuclei to overcome the positive force repelling them from each other (protons), so they can get close enough to react.
What is Irradiation?
the exposure to radiation from a radioactive source
What is contamination?
the unwanted presence of radioactive atoms in or on another material
