Atomic structure

• What is an atom?

  The smallest part of a substance where the element is still distinguishable
• What is a proton?


  Positively charged subatomic particle, in the nucleus and has a relative atomic mass of one
• What is a neutron?


  Neutral subatomic particle, in the nucleus and has a relative atomic mass of one
• What is an electron?


  Negatively charged subatomic particle, orbits the nucleus in shells and has a relative atomic mass of zero
• What is the atomic number?

  The number of protons and electrons in an atom
• What is the mass number?

  The number of protons and neutrons in an atom
• What did JJ Thompson discover?

  Electrons
• What is the plum pudding model and what led to its discovery?


  Negative electrons embedded in a sphere of positive charge, the electron led to its discovery
• What did Rutherford fire at Gold foil and what were the results?

  He fired Alpha particles at Gold foil. The results showed that some alpha particles passed straight through empty space and some were deflected backwards.
• List three conclusions from Rutherford’s experiments?

  Most of the atoms is empty space, tiny positively charged nucleus at the centre of the atom. most of the atoms is empty space, tiny positively charged nucleus at the centre of the atom. Most of the mass of the atom is concentrated in the nucleus.
• What did Neils Bohr discover?

  Electron shells
• What did James Chadwick discover?

  The neutron
• What is activity?


  Activity is the rate at which unstable nuclei decay, measured in becquerel
• What is count rate?

  The number of decades recorded per second by a Geiger- muller tube
• What is the approximate size of an atom?

  10^-10 meters
• What is the approximate size of a nucleus?

  10^-14 metres
• How can an electron move up an energy level of an atom?

  The absorption of an electromagnetic wave
• How do you give off a gamma particle/wave?

  An excited electron falls back down, giving off an electromagnetic wave in the form of a gamma wave
• What is an alpha particle?


  Two protons and two neutrons
• What is a beta particle?

  A fast moving electron
• What is a gamma par ?

  A high frequency electromagnetic wave
• Radiation will be admitted when an atom has too much what?

  Energy
• Define isotope?


  Atoms of the same element with different numbers of neutrons.
• How do you workout Alpha decay?


  You -4 from the mass number and then you -2 from the atomic number
• how do you workout beta decay?


  The mass number stays the same and for the atomic number you add one
• What is a beta particle stopped by?

  Aluminium or lead
• What change does a gamma particle have on a nucleus?


  None
• what is a gamma particle stopped by?


  Thick lead or concrete
• what is an alpha particle stopped by?

  A thin piece of paper
• What is the definition of half-life?

  The time it takes the number of radioactive nuclei in a sample to decrease by 50%
• Write a description as to how you use a graph to find half-life?


  Find a starting activity/count rate, halve this value using a ruler horizontally until you meet the graph line, then you use a ruler and go vertically to read off the X axis
• What is contamination?


  The unwanted presence of radioactive material
• What is irradiation?


  The process of being exposed to radiation