Atomic Structure

• What can the nucleus of an atom be split into?

  Smaller particles
• What was the first particle discovered in the nucleus?

  Positive proton
• Who proved the existence of neutrons?

  James Chadwick
• What does the plum pudding model represent?

  A sphere of positive charge with electrons
• What does the nuclear model of the atom describe?

  A positively charged nucleus with electrons around
• What did Niels Bohr's theoretical calculations support?

  Electrons orbiting the nucleus at certain distances
• What happens when electrons emit EM radiation?

  They move to lower energy levels
• What is the charge of neutrons?

  0 charge
• What is the charge of electrons?

  -1 charge
• What is the charge of protons?

  +1 charge
• What is the overall electric charge of an atom?

  Zero
• What does the alpha scattering experiment demonstrate?

  The nucleus is positively charged
• Where is most of an atom's mass concentrated?

  At the nucleus
• How much smaller is the nuclear radius compared to the atom's radius?

  About 10,000 times smaller
• What are the three types of nuclear radiation?

  Alpha, beta, gamma
• What does alpha radiation consist of?

  2 neutrons and 2 protons
• What is beta radiation?

  Fast-moving electron from the nucleus
• What is gamma radiation?

  Electromagnetic radiation from the nucleus
• What absorbs alpha radiation?

  Sheet of paper
• What absorbs beta radiation?

  Sheet of aluminium
• What absorbs gamma radiation?

  Thick sheets of lead
• What is the range of alpha particles in air?

  Few centimetres
• What is the range of beta particles in air?

  Few metres
• What is the range of gamma radiation in air?

  Longer distances
• What is radioactive decay?

  When an unstable nucleus decays into another element
• What is ionising radiation?

  Radiation that knocks electrons off atoms
• What are isotopes?

  Atoms with the same protons but different neutrons
• What is the atomic number?

  Number of protons in an atom
• What is the mass number?

  Total number of protons and neutrons
• What happens to mass and charge during alpha decay?

  Mass decreases, charge decreases
• What happens to mass and charge during beta decay?

  Mass stays the same, charge increases
• What is the half-life?

  Time taken for the number of nuclei to halve
• What is radioactive contamination?

  Unwanted radioactive atoms on or in an object
• What is irradiation?

  Exposure of an object to nuclear radiation
• What are the precautions against irradiation?

  • Keep sources in lead-lined boxes
  • Stand behind barriers or in a different room
  • Handle sources with remote-controlled arms
• What is nuclear fusion?

  Two light nuclei collide to form a heavier nucleus
• What is background radiation?

  Low-level radiation always present around us
• What are the two types of sources of background radiation?

  Natural and man-made sources
• What is radiation dose?

  Measure of risk of harm from radiation exposure
• How is ionising radiation used in radiotherapy?

  To kill cancer cells