Aims of this episode:

  • Understand what an atom is and what it is made of;
  • Describe the differences between elements, mixtures and compounds;
  • Be able to use the periodic table.


Atoms were once thought to be the smallest things in the Universe and they make up everything. Atoms are however, made from smaller particles (protons, neutrons and electrons), but they still make up everything you see around you.

The protons and neutrons are in the centre of the atoms (the nucleus) and the electrons are on the outside. The majority of an atom is actually empty space. Click here for a mind blowing TEDEd video.


Elements are substances made from just one type of atom. This means that every atom in the substance has the same number of protons, neutrons and electrons. All the atoms in the Universe are listed in the periodic table, along with their mass (massive) number – the number of protons + the number of neutrons; and their atomic number – the number of protons. The number of electrons will be the same as the number of protons (the atomic number).


These are when you take two or more elements and simply mix them together. The different atoms don’t chemically bond, so you can still separate the two elements.


Two or more elements chemically bonded together. This time you cannot simply separate the different atoms; they are chemically joined to one another. For example, H2O and CO2 are both compounds.

S@S 004: Atoms, Elements and Compounds
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