IB Chemistry - Bonding

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Syllabus reference

Structure 2.4.2 - The position of a compound in the bonding triangle is determined by the relative contributions of the three bonding types to the overall bond.

  • Determine the position of a compound in the bonding triangle from electronegativity data.
  • Predict the properties of a compound based on its position in the bonding triangle.


  • To illustrate the relationship between bonding type and properties, include example materials of varying percentage bonding character. Only binary compounds need to be considered.
  • Calculations of percentage ionic character are not required.
  • Electronegativity data are given in the data booklet.

Tools and links

  • Structure 2.1, Structure 2.2, Structure 2.3 - Why do composites like reinforced concretes, which are made from ionic and covalently bonded components and steel bars, have unique properties?

Classification of bonding

Nowadays there are many different types of materials in everyday use in society and industry, all of which have been specifically designed and manufactured for their intended purpose.

We have come a long way from stone and wooden tools! An understanding of the underlying structure of the materials and its consequences in terms of property has been essential in this process.

From the previous sections on ionic, covalent and metallic bonding we have seen how the structure influences the physical property of the material. However, the concepts of bonding can get blurred around the edges, as covalent compounds can exhibit a degree of ionic behaviour in terms of polarity, while ionic compounds can exhibit a degree of covalent character. We see that the classification of matter becomes more of a gradual change from one bonding type to another with a commensurate gradual change of property.

This gives rise to the term "bonding continuum", where boundaries between the major structural types are not well defined.

Napoleon's army and the Russian campaign of 1812

There is a theory that degradation of the properties of tin due to the cold, contributed to the defeat of Napoleon's army in the winter of 1812.

The story goes that the army uniforms were held together by buttons made of tin. Under normal European conditions this was just fine and the buttons did their job.

However, in the harsh Russian winter the low temperatures caused the tin to change from the metal allotrope to a non-metal allotrope (alpha tin), with disasterous consequences on its properties.

The buttons lost their hardness and became soft and crumbly. They fell apart, as did the soldiers' uniforms.

While this may just be an "urban legend", it highlights the link between structure and property in terms of materials.


The van Arkel Ketelaar bonding triangle

The bonding triangle shows us how to predict the type of bonding within a structure by referring to the electronegativities of the bonded elements.

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Mixtures and composites


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ColSol Testing