Structural units refer to the individual components that make up a larger structure, while repeating units refer to the smallest unit that is repeated to create the overall structure. In other words, structural units make up repeating units, which in turn make up the overall structure.
Structural units are related to repeating units in that they are the building blocks for the repeating units. Without structural units, the repeating units could not exist and therefore, the overall structure would not exist.
An example of a structural unit could be a carbon atom, while a repeating unit for a polymer could be a monomer made up of multiple carbon atoms. Another example could be a brick as a structural unit and a wall made up of multiple bricks as a repeating unit.
The arrangement and type of structural units and repeating units in a material determine its physical and chemical properties. For example, a polymer made up of repeating units with strong covalent bonds will result in a strong and durable material, while a polymer with weak intermolecular forces between repeating units will result in a more flexible material.
Yes, structural units and repeating units can differ in size. Structural units can be small molecules, atoms, or even larger complexes, while repeating units can be made up of multiple structural units. For example, a protein made up of amino acids as structural units can have repeating units of multiple amino acids to form a larger protein structure.