GCSE Combined Science (AQA)

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Bohr Model

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Atomic structure Atoms and isotopes

Bohr Model

2:36 History of the Atom
Spec 4.4.1.3
Previous Alpha Scattering Next Discovery of Protons & Neutrons
  • Rutherford's nuclear model states that atoms consist of electrons orbiting a nucleus.
  • Electrons orbit around a central, positive, massive nucleus.
  • In 1913, Neil Spore refined this model, theorizing that electrons can only orbit at set distances.
  • These set orbits are referred to as shells.
  • The orbit an electron occupies corresponds to its energy level; lower energy electrons are in lower orbits, higher energy electrons in higher orbits.
  • Electrons can change orbits by gaining or losing energy through electromagnetic radiation.
  • An electron moves to a higher orbit by absorbing the exact amount of energy needed from electromagnetic radiation.
  • An electron can move to a lower orbit by releasing electromagnetic radiation.
  • Theoretical calculations used by Boar to determine these energies matched experimental observations of radiation from hydrogen.
  • Electromagnetic radiation's wavelength, which determines its energy, can be measured.
  • Boar's Theory is supported by the properties matching calculations and the observation of only certain wavelengths of radiation from hydrogen.
  • Boar's calculations were incorrect for larger atoms; the method used for hydrogen did not work for them.
  • Despite inaccuracies for larger atoms, parts of Boar's Model are still applicable, such as fixed energy levels and emission of certain wavelengths.
  • At the GCSE level, it is not required to know the details of electron arrangements in larger atoms, but Boar's model is assumed to still apply.

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