Atomic structure Flashcards
Briefly explain how the model of an atom has changed over time
First thought atoms were tiny spheres that couldnt be broken up. Then the plum pudding model was discovered suggesting they were small spheres of positive charge with electrons in them. This was proven wrong when the first nuclear model of the atom was discovered.
What happens to an electron in an atom if it releases EM radiation
It will move to a lower energy level closer to the nucleus. Opposite if it absorbs EM radiation.
Who provided evidence to suggest the existence of the neutron
James Chadwick
What happens to an atom if it loses one or more is electrons
It becomes a positive ion
Which number defines what element an atom is
The atomic number
What is the atomic number of an atom and what is the mass number of an atom
The atomic number is the number of protons in an atom. The mass number is the number of protons + number of neutrons (mass of nucleus)
What is an isotope and are they usually stable
Isotopes of an elements are atoms with the same number of protons but a different number of neutrons. Most elements only have on or two stable ones others decay.
What is radioactive decay
The decay of unstable isotopes that give out radiation as they try to become more stable
Name four things that may be emitted during radioactive decay
Alpha radiation
Beta radiation
Gamma radiation
Neutrons
For the three types of ionising radiation give: Their ionising power and range in air
Alpha-Strongly ionising, only a few cm in air
Beta-moderately ionising, a few metres in air
Gamma-weakly ionising, will travel a long distance through air
Explain why alpha radiation could not be used to check the thickness of metal sheets
Alpha radiation is immediately absorbed by the material
What type of nuclear decay doesnt change the mass or charge of the nucleus
Gamma rays
What is the activity of a source and what are its units
The rate at which a source decays, measured in becquerels Bq (1 Bq is 1 decay per second)
Define half life
Half life is the time taken for the number of radioactive nuclei in an isotope to halve.
What does a short half life mean
A short half life means activity falls quickly because nuclei are unstable and decay quickly. High amounts of radiation are emitted at the start
Explain the dangers of a radioactive source with a long half life
It releases small amounts of radiation for a long time, therefore nearby areas are exposed to radiation for millions of years.
Explain how you would find the half life of a source given a graph of its activity over time
The half life is found from the graph by finding the time interval at the halving of the activity on the vertical axis
Define radiation dose
It tells you the risk of harm to body tissue due to exposure to radiation measured in sieverts
State two aspects of your lifestyle that can affect your radiation dose
Where you live and if you have a job that involves radiation
Define irradiation and contamination
Irradiation-Objects near a radioactive source are irradiated by it, meaning they are exposed to it.
Contamination-When unwanted radioactive atoms get onto or into an object
Compare the hazards of being irradiated and contaminated by an alpha source and a gamma or beta source
Beta and gamma sources are most dangerous outiside the body as it can penetrate the body and get to the delicate organs.
Alpha radiation is most dangerous inside the body as they do all their damage in a very localised areas.
Give two examples of how to protect against contamination and irradiation
Irradiation-keeping sources in lead lined boxes, standing behind barriers or being in a different room
Contamination-Gloves and tongs should be used when handling sources, protective suits should be worn to prevent particles being breathed in.
Describe some of the risks involved with using radiation
Radiation can enter living cells and ionise atoms and molecules with them which can lead to tissue damage.
Lower doses tend to cause mutant cells (cancer) and higher doses tend to kill cells completely causing radiation sickness
Give two ways that radiation is used in medicine
Medical tracers-Radioactive isotopes can be injected into people and their progress around the body can be followed.
Radiotherapy-Gamme rays are directed carefully and at just the right dosage to kill the cancer cells without damaging too many normal cells.
