unit 3.1

• Three sub-atomic particles found inside atoms:

  • Electrons
  • Protons
  • Neutrons
• Protons and neutrons are found in the nucleus at the center of the atom
• Electrons, with negligible mass, move rapidly around the nucleus
• Most of the mass of an atom is concentrated in its nucleus because it contains protons and neutrons
• All atoms are electrically neutral
• Particle: Proton

  Symbol: p

  Relative mass: 1

  Relative charge: +1

  Location in the atom: Nucleus
• Particle: neutron

  Symbol: n

  Relative mass: 1

  Relative charge: 0

  Location in the atom: nucleus
• The number of electrons equals the number of protons
• The relative atomic mass (A) is calculated by adding up the number of protons and neutrons in the nuclei
• all atoms are electronic neutral
• atomic number = number of protons