Atomic Model

  • Created by: sara.5
  • Created on: 24-04-18 18:51
Who introduced the particle theory and in what year?
John Dalton 1305
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What is the particle theory?
A model that helps us explain properties of solid, liquid and gases.Particles are represented as spheres
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What did JJ Thomson discover?
The subatomic particles called electron
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Which atomic model did Thomson introduce?
The Plum Pudding model
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What is the Plum Pudding model?
Using the idea of subatomic particles Thomas suggested this model of atom in 1904.The plum pudding describes an atom as a 'pudding' made of positively charged material with negatively charged electrons 'plums' scattered through it
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Between 1909-13 why did Rutherford carry out an experiment?
To investigate the structure of an atom.
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What did the experiment consist of?
Rutherford team firing Alpha particles at thin gold foil
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What did they found out?
That the Alpha particles passed through the gold foil, but few bounced back
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Why was this?
As they bumped into the nucleus
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What did Rutherford suggest?
Atoms were mostly empty space with most of their mass in a tiny central nucleus with a positive charge and electron moving around the nucleus
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What are the certain orbits called that the electron can exist?
Electron shells
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What happens when an atom absorb energy?
The electron jump to higher shells
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What happens when they fall back?
They emit energy as an Electromagnetic Radiation that we can see
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The emission is different for each...
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What did Neil Bohr amend in Rutherford's model?
He suggested electrons can only be in fixed orbits (shells) around the nucleus.They cannon be in between
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What can models explain?
The line in emission and absorption spectrum
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what happens when a atom gains so much energy?
One or more electrons can escape from the atom altogether.A atom that has gained or lost and electron is called an ion
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What is the radiation that causes electrons to escape?
Ionising Radiation
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What is meany by Background Radiation?
Ionising radiation that is around us all the tome from a number of sources.Some are naturally occurring but some come from human activities
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What are some sources of background radiation?
Radon Gas,Food and drink,Cosmic Ray,Ground and building,Medical
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What is the main source of Background radiation?
Radon Gas
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What is it produced by?
A rock that contains Uranium.Radon diffuse into air from rock and soils and can build up in houses especially if there is poor ventilation.The amount of Radon depends on the type and its uranium content
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How can radioactivity of a source be measured?
Using a Geigermuller (GM ) Tube.
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How does it work?
Radiation passing through the tube ionises gas inside it and allows short pulse of current to flow
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What is meant by the Count Rate?
The number of clicks per second/minute
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What are the property of the Alpha Particle?
Very large ionising effect but only travel a few centimetre in air from nucleus. Stopped by a sheet of paper.Just like helium atom. 2neutrons. Ram of 4
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What are the properties of Beta particles?
Travel a few centimetre in air and has a moderate ionising effect.Stopped by 3mm aluminium thick aluminium
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What are the properties of Gamma particles?
Travel several Kms in air and only have small ionising effect.Need thick lead or several metres of concrete to stop them.
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What is meant by penetration?
The ability to pass through a material
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What happens to a Beta minus decay?
A neutron changes into proton and a electron.Electron is ejected from nucleus
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What happens in a Beta positive decay?
Proton become neutron or positron
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What is meant by half life?
The time taken for half of the unstable nuclei in sample a radioactive isotope to decay
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Why can we not predict the decay of an individual nucleus?
as it is a random process
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How does the half life allow us to predict the activity of a large number of nuclei?
The more stable a nuclei a sample of a substance contains, the lower its activity
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What is the activity of any radioactive substance ?
The number of nuclear decays per second is measured in becquerels
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What can a large amount of radiation cause?
Tissue damage such as reddened skin(radiation burns) and also other effects that cannot be seen
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What can small amounts of ionising radiation do over long time?
Damage the DNA inside a cell.Or in other words mutations.Mutations can cause cells to malfunction and some mutation can cause cancer.Gene gametes can be passed on to the next generations. But if the dose is low cells could often repair the damage
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Why is radiation a hazard?
Because it can cause harm
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What sort of people need to take precautions to minimise risks from radiation?
People who work with radioactive materials are exposed to more radiations
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How can the intensity of radiation be decreased?
By increasing distance from the source so sources are always handled with tongs
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How else can the risk of radiation be reduced?
By not pointing sources at people and storing them in lead lined container
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How do medics who work with radioactive sources limit their exposure?
Increasing distance from source, shielding the source and minimising the time spent in the presence of sources, Their exposure is closely monitored using dosimeter
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Why are some patients exposed to a dose of radiation for medical diagnosis?
This is only done when the benefits are greater than the possible harm the radiation can cause and the minimum possible dose is used
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What happens if there is an accident in the nuclear power station?
Radioactive materials escape in the environment
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How can these sort of accident cause a hazard?
They may lead to people being irradiated or contaminated
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What is irradiated?
When they are exposed to alpha,beta or Gamma radiation from nearby radioactive materials.Once the person moves away the radiation stops
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What is Contaminated?
If they get particles of radioactive material on their skin or inside their body.They will be exposed to radiation as the unstable isotope decays or until the source of contamination is removed.Water/soil can be contaminated and can spread into chain
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Other cards in this set

Card 2


What is the particle theory?


A model that helps us explain properties of solid, liquid and gases.Particles are represented as spheres

Card 3


What did JJ Thomson discover?


Preview of the front of card 3

Card 4


Which atomic model did Thomson introduce?


Preview of the front of card 4

Card 5


What is the Plum Pudding model?


Preview of the front of card 5
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