GCSE Chemistry (AQA)

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Development of the Later Atomic Models

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Atomic structure and the periodic table A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes

Development of the Later Atomic Models

3:47 Development of the Atomic Model
Spec 4.1.1.3
Previous Development of the Atomic Model Next Atomic Nucleus and Shells
  • The nuclear model of the atom has evolved over time based on experimental observations.
  • The alpha scattering experiment revealed that almost all the mass and positive charge of an atom are in a central nucleus.
  • The term "nuclear model" originates from this discovery.
  • Initially, electrons were thought to be scattered around the empty space of the atom.
  • Niels Bohr refined the model by proposing that electrons orbit the nucleus at specific distances, known as energy levels or shells.
  • Bohr's theory predicted behaviors and calculations that matched experimental observations.
  • Later experiments indicated that the nucleus's positive charge came from multiple smaller particles, not a single particle.
  • These smaller particles were named protons, which are positively charged and heavier than electrons.
  • James Chadwick's experiments discovered neutrons, particles in the nucleus with mass but no charge.
  • Neutrons explained inconsistencies in atomic mass measurements without affecting the charge.
  • The nuclear model with protons, electrons, and neutrons is the basis for current understanding and is used in GCSEs.
  • The understanding of atomic structure continues to become more detailed and refined.

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