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?
- Inside nucleus
- +1 charge
- mass of 1
- Inside nucleus,
- no charge
- mass of 1
- 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?
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
- Ground and buildings
- Food and drink
- Radon gas
- Cosmic rays
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?
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.
SP6e - Rank the types of radiation in terms of penetration / range.
- Gamma (Most)
- Beta (+/-)
- Alpha (Least)
SP6e - What does it take to stop each type of radiation?
- Alpha: paper/skin/few cm of air
- Beta: few m of air/3mm of alluminium
- Gamma: few Km of air/ few cm of lead/ several m of concrete
SP6f - What occurs in alpha decay?
An unstable nucleus looses 2 protons and 2 neutrons (an alpha particle) causing its mass number to decrease by 4 and its atomic number to decrease by 2.
SP6f - What occurs in beta minus decay?
A neutron decays into a proton and a high energy electron.
SP6f - What occurs in beta plus decay?
A proton decays into a neutron and a high energy positron.
SP6f - What occurs in gamma decay?
An unstable nucleus emits a gamma ray becoming more stable.