Atomic structure

• What is the radius of an atom?

  $1\ \times10^{-10}$
• What happens when an electron gains electromagnetic radiation?

  Moves further from the nucleus to a higher energy level
• What happens when an electron emits electromagnetic radiation?

  Moves closer to the nucleus , down an energy level
• What does the atomic number show?

  Number of protons and electrons in an atom
• What is the mass of an electron?

  1/2000
• What does the mass number show?

  The total number of protons and neutrons in an atom
• What is an isotope?

  An atom of the same element with a different number of neutrons
• What is an ion?

  A charged particle - when an atom gains or loses an electron
• What were atoms thought to be?

  Tiny spheres that could not be divided further
• Who discovered the electron?

  JJ Thompson
• What did the plum pudding model suggest?

  The atom is a ball of positive charge with negative electrons embedded in it
• What was the conclusion of the alpha scattering experiment?

  The mass of an atom is concentrated in the nucleus and it is charged
• Who carried out the alpha scattering experiment?

  Rutherford
• Why was Rutherford conclusions excepted?

  It was reproducible
• What were the observations made in the scattering experiment?

  • Most went through
  • Some deflected
  • Few reflected
• Which model replaced the plum pudding model?

  The nuclear model
• What did Bohr do?

  Suggested electrons orbit the nucleus in shells at specific distances
• What was discovered after Bohr's idea?

  Protons
• Who discovered the neutrons?

  Chadwick
• What are the differences between the plum pudding model and the nuclear model?

  • The plum pudding suggests electrons are scattered in a positive ball whereas nuclear suggests they are in shells
  • Plum pudding suggests mass is equally distributed whereas nuclear suggests mass is concentrated in the nucleus
  • Plum pudding doesn't show neutrons
• What is radioactive decay?

  When a nucleus gives out radiation as it changes to become more stable. This is a RANDOM process
• What is activity?

  The rate at which a source of unstable nuclei decays
• What is activity measured in?

  Becquerel Bq
• What is the count rate?

  the number of decays recorded each second by a Geiger Muller tube
• What does an alpha particle emit?

  Two neutrons and Two protons (Helium nucleus)
• What are the properties of an alpha particle?

  • High ionising power
  • Low penetrating power
  • Stopped by paper
  • Low range in air
  • +2 charge
• What does a beta particle emit?

  A high-speed electron ejected from the nucleus as a neutron turns into a proton
• What are the properties of a beta particle?

  • Mid range in air
  • Mid penetrating power
  • Stopped by aluminum
  • Mid inioing power
  • -1 charge
• What does a gamma ray emit?

  No mass or charge
• What are the properties of gamma rays?

  • Very short wavelength
  • High frequency
  • Low ionising power
  • Stopped by thick lead
  • High range in air
  • High penetrating power
• What is a half-life?

  The time it takes for the number of nuclei of the isotope in a sample to halve
• What is radioactive contamination?

  The unwanted presence of materials containing radioactive atoms on other materials
• What is irradiation?

  The process of exposing an object to nuclear radiation. The object does not become radioactive
• What are the different precautions that can be taken to protect from radiation?

  1. Shielding (gloves, suits, lead)
  2. Monitoring
• What is the term when other scientists share and publish their findings with others?

  Peer Review
• Where does background radiation come from?

  1. Natural sources such as rocks and cosmic rays from space
  2. Man- made sources such as the fallout from nuclear testing and accidents
• What is radiation dose measured in?

  Sieverts
• 1000 mSV=

  1 Sv
• What is nuclear fission?

  The splitting of a large, unstable nucleus into 2 smaller, less unstable daughter nuclei
• For fission to occur, what must the unstable nucleus do?

  Absorb a neutron