Atoms and Sub-Atomic Particles

• How big are atoms?

  • The radius of atoms is approximately 0.1 nanometres, or 1x10-10 m.
  • About 5 million hydrogen atoms could fit into a pin head.
  • The nucleus of an atom is 10,000 times smaller than the atom.
  • If an atom was the size of Wembley Stadium, then the nucleus would be the size of a garden pea.
• Relative mass

  • Sub-atomic particles:
  • Relative mass of protons and neutrons = 1
  • Relative mass of electrons = 0.0005 (this gets rounded to zero)
  • Atoms:
  • Relative mass = number of protons + number of neutrons