Atoms

• Isotopes are atoms with different numbers of neutrons but the same number of protons, resulting in slightly different masses.
• 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
• Atom


  The smallest part of an element that can exist
• Particle


  A general term for a small piece of matter. For example, protons, neutrons, electrons, atoms, ions or molecules
• Dalton's model of the atom

  • All matter is made of tiny particles called atoms
  • 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


  • Protons
  • Neutrons
  • 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
• Atoms are tiniest particles of matter that can exist. They are made up of protons, neutrons and electrons.
• John Dalton
• Thompson discovered the electron by using cathode ray tubes to investigate the nature of electricity.
• Dalton's atomic theory states that all matter is composed of tiny indivisible particles called atoms. Each type of atom has its own unique properties such as size, mass and chemical reactivity.
• The discovery of the neutron led to the development of nuclear physics and our understanding of radioactivity.