Atoms

• Everything whether it's living, non-living or even a cell itself is made up of lots of tiny particles which we call atoms
• A single cell probably contains more than 100 trillion atoms
• Atom

  A central nucleus surrounded by electrons which orbit around the nucleus in rings that we call shells
• Particles that make up an atom

  • Protons
  • Neutrons
  • Electrons
• Protons and neutrons

  • Have the same mass, with a relative mass of 1
  • Protons have a positive charge of 1+
  • Neutrons have no charge (are neutral)
• Electrons

  • Have a mass 2000 times smaller than protons and neutrons
  • Have a negative charge of 1-
• The size of an atom depends on which element it is
• Atoms have a radius of around 0.1 nanometers
• Most of an atom is actually empty space
• The nucleus is 10,000 times smaller than the width of the atom
• The electrons are even smaller than the nucleus
• Ion

  An atom that has lost or gained electrons, so the positive and negative charges no longer balance
• Types of ions

  • Negative ion (more electrons than protons)
  • Positive ion (more protons than electrons)
• The periodic table represents different types of atoms, which we call elements
• Atomic number

  The number of protons in an atom, which determines the element
• Mass number

  The total number of protons and neutrons in an atom
• The number of protons and electrons in an atom is always the same
• Atom

  Made up of a central nucleus which comprises protons and neutrons, and electrons orbiting that nucleus