GCSE Combined Science (AQA)

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Discovery of Protons & Neutrons

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Atomic structure Atoms and isotopes

Discovery of Protons & Neutrons

1:39 History of the Atom
Spec 4.4.1.3
Previous Bohr Model Next Alpha Decay Equations
  • The alpha scattering experiment demonstrated that atoms have a small charged nucleus.
  • The nucleus contains almost all the atom's mass and is positively charged.
  • Electrons, which are negatively charged, orbit around the nucleus.
  • The positive charge of the nucleus cancels out the negative charge of the electrons, resulting in no overall charge for the atom.
  • Scientists later discovered that the nucleus's positive charge is composed of smaller particles called protons.
  • The discovery of protons led to the understanding that protons and electrons have equal and opposite charges.
  • In 1932, James Chadwick discovered neutrons, uncharged particles within the nucleus.
  • Neutrons are similar in mass to protons but have no charge, making them difficult to detect.
  • The presence of neutrons explains why elements can have varying masses and led to the concept of isotopes, which are versions of the same element with different masses.

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