Corundum is an example of ionic bonding not covalent bonding. We have changed the following paragraph to reflect this and also changed the word 'sharing' or 'shared' to 'donating' or 'donated'.
For a molecule of corundum, the donation of electrons allows for the ionic bonding of the atoms to form a compound. Since aluminium has three electrons in its outer valence level, we will need three oxygen atoms (each requiring two electrons, six electrons in total) to supply electrons to the two aluminium atoms. This will ensure that both oxygen and aluminium atoms have stable outer orbitals of eight electrons each. In the example (Figure 1.9), one aluminium atom has donated three electrons, one electron to the first oxygen atom and two electrons to the second. The other aluminium atom has also donated three electrons, one to the first oxygen atom and two to the third oxygen atom.
The diagram should say 'Tungsten' not 'Tungten'
The diagrams should say 'Examples of SI-1 and Examples of SI-2'
Minor adjustments have been make to the Figure 2.10 - Diamond & Graphite Atom Arrangements (changing the positioning of one of the arrows), Figure 3.8 - Interference of Light (the ray entering the water is refracted and then reflected) and Figure 6.14 - Biaxial Optic Signs (on the biaxial negative diagram, the shadow edge has been moved so that it is less than half-way).