Image Water molecule

TLF ID R6843

This is a colour image of a model of a molecule of water, H₂O. In this model, atoms are represented by coloured spheres held together by grey rods, representing covalent bonds. The water molecule contains one oxygen atom (the red sphere) and two hydrogen atoms (the grey-white spheres).



Educational details

Educational value
  • Water is a chemical compound found on Earth in solid, liquid and gaseous states. All three states contain the same molecules but their arrangement and spacing differ in each state. It is one of the rare substances for which the solid state is less dense than the liquid at its melting point, so that ice floats in water. Water has the ability to dissolve many other substances and this is one reason why it is so essential to living things.
  • The atoms in the water molecule are connected by single covalent bonds. A covalent bond is formed when atoms share electrons. A single covalent bond has two shared electrons, one contributed by each atom. Because the oxygen atom is able to contribute two electrons, it is able to participate in two covalent bonds, whereas each hydrogen atom has only one electron to share and so can form only one bond.
  • The electrons in these bonds are not shared equally; they are attracted more strongly to the oxygen. This, combined with the 104.5-degree angle between the bonds, results in the water molecule having an electric dipole, and consequently water molecules are strongly attracted to each other. This unusually strong attraction is termed ‘hydrogen bonding’ and is responsible for water’s solvent properties, high boiling point and high surface tension.
  • The type of model shown here, called a ball-and-stick model, is one of several ways of modelling molecules. This type is useful because it clearly shows the geometry of the molecule and the order (single, double or triple) of the bonds. However, because 'sticks' are used to represent bonds, this type of model does not represent the actual shape of the molecule as well as 'space-filling' models do.

Other details

Contributors
  • Publisher
  • Date of contribution: 20 Sep 2013
  • Organisation: Education Services Australia
  • Address: Melbourne VIC 3000 Australia
  • URL: http://www.esa.edu.au/
  • Copyright holder
  • Organisation: Education Services Australia
  • Address: Melbourne VIC 3000 Australia
  • URL: http://www.esa.edu.au/
  • Remarks: Copyright Education Services Australia
  • Author
  • Date of contribution: 2006
  • Organisation: Education Services Australia
  • Address: Melbourne VIC 3000 Australia
  • URL: http://www.esa.edu.au/
  • Remarks: creator
  • Content provider
  • Organisation: Education Services Australia
  • Address: Melbourne VIC 3000 Australia
  • URL: http://www.esa.edu.au/
Access profile
  • Device independence
  • Hearing independence
Learning resource type
  • Image
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Rights
  • © Education Services Australia Ltd, 2013, except where indicated under Acknowledgements.