C4 Science

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The Nucleus

  • It's in the middle of the atom
  • It contains protons and neutrons
  • It has a positive charge because of the protons.
  • Almost the whole mass of the atom is concentrated in the nucleus
  • But size-wize it's tiny compared to the rest of the atom

The Electrons

  • Move around the nucleus
  • They're negatively charged.
  • They're tiny, but they cover a lot of space.
  • The volume of their orbits determines how big the atom is.
  • They have virtually no mass
  • They're arranged in shells around the nucleus


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Atoms - Particles


  •  Protons are heavy and postively charged
  • Neutrons are heavy and neutral
  • Electrons are tiny and negatively charged

The number of Protons Equals number of Electrons

  • Neutral atoms have no charged overall
  • The charge on the electrons is the same as the charge on the protons - but opposite.
  • This means the number f protons always equals the number of electrons in a neutral atom.
  • If some electrons are added or removed, the atom becomes charged and is then an ion
  • The number of neutrons isn't fixed but is usually about the same as the number of protons

Atoms of the same element all have the same number of protons - and atoms of different elements will have different numbers of protons.

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