SP6 - Radioactivity ✓
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SP6a - What did the plum pudding model look like?
Made of positively charged mass with negatively charged electrons scattered throughout.
SP6a - What was the experiment that Erenest Rutherford conducted and what did he do?
• The gold foil experiment. • He fired alpha particles through various substances e.g. thin gold foil. • Firing alpha particles from a source and having a detector behind whatever substance he used so that he could find out if the particles pass through.
SP6a - What were the results drawn of the gold foil experiment and what conclusions were drawn from this?
• Most particles passed straight through • Some were deflected slightly • Others were bounced back • This means that most of an atom is empty space. • Aditionally, atoms have a concentrated area of positive charge. • This is why some were reflected back.
SP6a - What is the radius of a nucleus and the radius of an atom?
• N: 1x10-15 • A: 1x10-10 (Atom is 10,000 times bigger)
SP6b - What are the charges, locations and relative masses of protons neutrons and electrons?
P: • Inside nucleus • +1 charge • mass of 1 N: • Inside nucleus, • no charge • mass of 1 E: • Orbiting nucleus • -1 charge • mass of 1/1835 (negligible)
SP6b - What does the atomic number of an atom represent?
• The number of protons in the nucleus. • Different elements have different proton numbers
SP6b - What does the mass number of an atom represent?
• The mass of the atom. • Protons plus neutrons.
SP6b - What is an isotope?
Two atoms of the same element with different masses (Same atomic number but different mass numbers)
SP6c - What can happen if an atom gains enough energy and what does this create?
• An electron can move to a higher orbit. • When it returns back to its orbit it emits energy in the form of visible light. • The wavelength (and therefore colour) depends on the change in orbit.
SP6c - What do we use to see the light produced by an atom?
• An emission spectrum. • A black line spectrum with coloured lines along it displaying which wavelengths were emitted.
SP6c - How will the emission spectrum of an element relate to its absorption spectrum and what does this tell us?
• The coloured areas on the emission spectrum will be blacked out on the absorption spectrum and vice versa. • This means that the wavelengths that are emitted are also the wavelengths that are absorbed.
SP6c - If an atom gains more energy than needed to just move an electron to another orbit, what can happen and what is this called?
• The atom can loose an electron. • This is called ionisation as the atom has become an ion
SP6c - What is an ion?
An atom that is charged due to a gain or loss of electrons.
SP6c - What do we call radiation that causes an atom to loose an electron?
Ionising radiation
SP6d - What is background radiation?
Radiation that is constantly all around us at a safe level.
SP6d - What are the six main sources of background radiation
• Medical • Ground and buildings • Food and drink • Radon gas • Cosmic rays • Nucelar
SP6d - Which source of backgrond radiation accounts for most of it and approximately how much is it?
Radon gas just under 50%
SP6d - What are ways of measuring radioactivity?
• With a Geiger • Mueller tube / counter Meausres the count rate • Photographic film (badges called dosimeters) Gets darker / changes colour as its exposed to more radioactivity
SP6d - Before measuring the radioactivity of a source what must be done?
Measure the background radiation so you can take this away from the radiation that you measure or else you value will be the source’s radiation + the background radiation.
SP6e - What is an alpha particle?
A helium nucleus consisting of 2 protons and 2 neutrons
SP6e - What is a beta minus particle?
An electron
SP6e - What is a beta plus particle?
A position (A positive electron)
SP6e - What don’t gamma rays have that other radiation does.
Since it is an EM wave and not a particle, it doesn’t have a charge.
SP6e - Rank and explain the types of radiation in terms of ionisation.
• Alpha (Most) • Beta (+/-) • Gamma (Least) Since alpha particles are emitted at high speeds thay carry most energy and are best at ionistation. This is the opposite for Gamma.