Atoms and isotopes

• What are the three subatomic constituents of an atom

  • Proton
  • neutron
  • electron
• Where is most of the mass of an atom concentrated

  In the nucleus
• Describe the arrangements of protons, neutrons and electrons

  • The protons and neutrons are found in the atoms nucleus
  • the electrons are found in discrete energy levels around the nucleus
• What type of charge does the nucleus of an atom have and why

  • Positive charge
  • the nucleus contains protons and neutrons
  • protons have a positive charge
  • neutrons have no charge
• Give two ways that an atoms electron arrangement can be changed

  1. Absorbing electromagnetic radiation
  2. emitting electromagnetic radiation
• Explain how an atoms electron arrangement changes when it absorbs EM radiation

  • Electrons move further away from the nucleus
  • they move to a higher energy level
• Explain how an atoms electron arrangement changes when it emits EM radiation

  • Electrons move closer to the nucleus
  • they move to a lower energy level
• How does the ratio of electrons to protons in an atom result in the atom having no overall charge

  • The number of protons is equal to the number of electrons
  • protons and electrons have equal and opposite charges, so charge cancels
• What do all forms of the same element have in common

  They have the same number of protons
• What’s the name given to the number of protons in an atom

  Atomic number
• What’s an atoms mass number

  The total number of protons and neutrons in the atom
• What’s an isotope of an atom

  An atom of an element that has a different number of neutrons but the same number of protons
• How do atoms turn into positive ions

  • They lose one or more of their outer electrons
  • electrons are negatively charged so the resultant charge of the atom is positive
• What may lead to a scientific model being changed or replaced

  The discovery of new experimental evidence which doesn’t agree with the existing theory
• How did the plum pudding model describe the atom

  A ball of positive charge with negatively charged electrons distributed evenly throughout it
• Prior to the discovery of the electron what was believed about the atom

  The atom was believed to be indivisible
• Which experiment led to the plum pudding model

  Rutherfords alpha scattering experiment
• What the name given to the currently accepted model of the atom

  The Bohr nuclear model
• State the conclusion of the alpha scattering experiment

  • Most of the mass of the atom is concentrated at the centre in the nucleus
  • the nucleus is positively charged
• What reinforces a scientific theory

  When experimental results agree with the hypothesised theoretical calculations and theorise
• What did James Chadwick’s experiments on the atom prove

  The existence of neutrons