Topic 4 - Atomic Structure Flashcards
Briefly describe how the model of an atom has changed over time.
- Democritus made the theory that matters is made up of tiny spheres known as ‘atoms’
- Thomson introduces the plum pudding model with spheres of positive charge and tiny negative electrons stuck to them
- Rutherford discovered the nucleus through performing an experiment of firing alpha particles at a thin gold foil
- Bohr refined Rutherford’s nuclear model and made the conclusion that electrons orbited the nucleus in ‘energy levels’ or shells
- Chadwick discovered the neutron.
Who provided evidence to suggest the existence of the neutron?
James Chadwick
True or False? Atoms have no overall change.
True
What happens to an atom if it loses one or more of its outer electrons?
It becomes a positively charged ion
Which number defines what element an atom is: The atomic number or the mass number?
Atomic number
What is the atomic number of an atom?
The number of protons
True or False? Isotopes have different mass numbers.
True
What is radioactive decay?
When unstable isotopes decay into other elements and give out radiation as they try to become more stable.
Name 4 things that may be emitted during radioactive decay.
- Alpha radiation
- Beta radiation
- Gamma radiation
- Neutrons
For alpha, beta, and gamma radiation, give: a). Their ionising power b). Their range in air
a). Alpha is strongly ionising, Beta is moderately ionising and gamma is weakly ionising
b). Alpha has a range of a few cm, Beta has a range of a few metres, and gamma has a long distance of range
Explain why alpha radiation could not be used to check the thickness of metal sheets.
It has a very weak penetrating power, and can be absorbed by a sheet of paper.
How could you represent alpha radiation in nuclear equations?
A helium nucleus (4/2 He)
What type of nuclear decay doesn’t change the mass or charge of the nucleus?
Gamma rays
Name a piece of equipment that could be used to measure radiation.
Geiger-Muller tube and counter
What is the activity of a source? What are its units?
The number of counts per minute (Bq)
Explain the dangers of a radioactive source with a long half-life.
The damaging effects of the radiation lasts too long and the dose received continues to rise.
Explain how you would find the half-life of a source, given a graph of its activity over time.
Read the initial activity off the graph. Divide the initial activity by 2 to find the value of half the initial activity. Find this value on the y-axis and read along horizontally to the curve. Then read down the curve at that point to find the half-life.
Define radiation dose.
The risk of harm to body tissues due to exposure to radiation (Sv).
State 2 aspects of your lifestyle that can affect your radiation dose.
- Occupation
- Location
Define irradiation and contamination.
Irradiation= Exposure to radiation
Contamination= Radioactive particles getting onto objects
Compare hazards of being irradiated by an alpha source and a gamma source.
Alpha is less dangerous because it can’t penetrate the skin and gets blocked by a small air gap, unlike gamma which is highly penetrable and can get to delicate organs.
Give 2 ways that radiation is used in medicine.
- Radiotherapy
- Medical Tracers
Describe some of the risks involved with using radiation.
Radiation can enter cells and ionise atoms and molecules within them, which can lead to tissue damage.
Define fission and fusion.
Fission = used to release energy from large and unstable atoms by splitting them into smaller atoms.
Fusion = when 2 light nuclei collide and join to create a larger nucleus.
True or False? Fission is usually spontaneous.
False
Describe what a chain reaction is.
refers to a process in which neutrons released in fission produce an additional fission in at least one further nucleus.
Explain the difference between nuclear fission and fusion.
In nuclear fusion, two nuclei of lighter elements combine to create a nucleus of a larger element, whereas in nuclear fission a large nucleus splits into two smaller nuclei
