chemistry - atomic structure

• Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in shells
• The numbers of particles in an atom can be calculated from its atomic number and mass number
• Dalton's model


  All matter is made of tiny particles called atoms, which are tiny solid balls
• Dalton's model


  • Atoms cannot be broken down into anything simpler
  • Atoms of a given element are identical to each other
  • Atoms of different elements are different from one another
  • During chemical reactions atoms rearrange to make different substances
• Dalton's model has changed over time because of the discovery of subatomic particles
• Subatomic particles


  Objects found in atoms, including protons, neutrons and electrons
• Atoms can be broken down into three smaller particles: protons, neutrons and electrons
• Atoms of an element have identical numbers of protons and electrons, but can have different numbers of neutrons
• Atoms of different elements have different numbers of protons and electrons
• In Dalton's time, the technology did not exist to discover the detailed structure of atoms