Ball and spoke models
Ball and spoke models are a common way of representing molecular structures. Each atom is represented by a coloured ball that is joined to other atoms using spokes to represent the bonds between them. This type of model emphasises the bonding between atoms.
Showing how atoms bond together
Each wooden ball has a number of holes drilled into it. These correspond with the number of bonds that the atom can form with other atoms. The number of bonds that can be made depends on how many electrons an atom has, which varies depending on the element. For example, oxygen atoms can make two bonds, but hydrogen atoms can only make one.
The chemist Wilhelm August Hofmann first used coloured balls to represent the elements around 1865. John Dalton, who in the 19th century made great advances in thinking about the structure of atoms, used ball and spoke models in his lectures. Some of his models and diagrams of atoms are displayed in the Science Museum in London.