For example, if the bonding in diamond, ice, MgO or CO2 is to determine, how can I find it out? How to determine van der Waals forces?
The basic types of chemical bonds are learned already at school: atomic bond (single bond, double bond, triple bond), ionic bonding, atomic bond with partial ionic character, metallic bonding. The first three mentioned types depend on the difference of electronegativity difference. Single bond, double bond and triple bond depend on the outer electrons (valence electrons) of the atoms involved in the chemical bond.
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At high school, you learn the octet rule and that there are also double bonds and triple bonds with partial ionic character.
At studying chemistry at the college, you learn the chemical bonds in the main chemical compounds. You learn that for some chemical bonds, more complex models are required that depend on the orbital structure. You also learn that the chemical bonds are only models for describing some facets of the chemical compounds and that for some chemical bonds there is no adequate model.
Van der Waals forces are only one kind of intermolecular forces. There are models for calculating them. In principle, intermolecular forces as a whole can today be measured by atomic force microscopy.