Atoms, Compounds and Molecules.


When you look at the periodic table of elements, you see a lot of letters. These letters represent elements. An element is one or many pure atoms. We determine an atom to be the “stuff” everything around us is made of. This “stuff” is what we would get if we kept on dividing everything into smaller and smaller chunks.

Periodic table - Wikipedia
Periodic Table of Elements from Wikipedia

An atom is composed of a nucleus (which contains protons and neutrons) as well as having this nucleus orbited by electrons. The number of protons will determine what element the atom will be. For example if the atom only contains one proton, the it will be an atom of the element hydrogen. If the atom contains 6 protons, it will be an element of carbon.

A molecule is multiple atoms of the same type which are chemically bonded together. A chemical bond keeps these together and changes the properties of the atom’s. For example, different chemical bonds join carbon’s together. One type of bonding is able to form graphite while the same atoms bonded in a different arrangement can form diamond. As you can see a soft grey compound is very different to a hard shiny one despite them both containing the same elements.

Compound are multiple different atoms joined together through chemical bonds, these can be represented using a formula. For example, carbon dioxide is a compound


Question 1.

Classify the following as elements, molecules or compounds

  1. Argon (Ar)
  2. Hydrogen gas (H2)
  3. Water (H2O)
  4. Oxygen (O2)
  5. Carbon Dioxide (CO2)
  6. Glucose (C6H12O6)
  7. Organesson (Og)
  8. Benzene (C6H6)
  9. Ozone (O3)

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