Atoms may form molecules. A molecule consists of two or more atoms joined together.


If atoms are of the same element, they form molecules of the element. If atoms of two or more elements are joined together by chemical bonds, they form molecules of a compound.

Molecules of Elements.

Most of the gases found on the periodic table will form a molecule.  They are diatomic elements.  This means that they are always joined to another atom of the same element.

The diatomic gas elements found at

room temperature are:






There are two liquid elements which are diatomic

elements at room temperature and they are:



Molecules of Compounds

A compound has a fixed composition. This means that every molecule of a compound has a particular set of elements and number of those elements that make it up.

Carbon dioxide (CO) contains one carbon atom and two oxygen atoms joined together.



Water (H2O) contains two hydrogen atoms and one oxygen atom joined together.

Sugar contains twelve carbon atoms, twenty two hydrogen atoms and eleven oxygen atoms joined together.


Table salt – sodium chloride (NaCL) has one sodium atom and one chlorine atom joined together.

You can have some fun building your own molecules.

You will need:


Jelly tots or marshmellows, or wine gums or any soft sweets.

1. Find two jelly tots which are the same colour and stick one on each end of a toothpick.  You have just made a molecule of an element!

2. To make a molecule of carbon dioxide:  Find two jelly tots which are green to represent oxygen and one which is red to represent the carbon.  Slide the red one into the center of the toothpick and stick each of the green ones onto the ends of the tooth pick.

3. To make a molecule of water, snap a toothpick on half.  Take two blue jelly tots to represent hydrogen and stick each one on the ends of your toothpicks.  Take a green jelly tot and stick the other end of your tooth picks into it at angles.  

Best of all you can eat them when you are done!

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All images sourced from unless otherwise stated