But properties of molecules depend not just on atomic composition, but also molecular structure. This complexity frustrated elemental analysis and supported the old idea of a life force, vitalism . This school of thought held that substances from living things could not be made artificially because they were imbued with a force or energy, the vital force . Gradually scientists appreciated that the structure of molecules helped determine chemical and physical properties. But as we shall see, all the large, complex molecules of life are assembled from smaller subunits, so the challenge of solving structures is very large but not impossible.
Chemical bonds involve the sharing of electrons between two atoms.
So the formation or breakage of a chemical bond involves interactions of atoms and their electrons . 3.5 Oxygen is much more electronegative than hydrogen, that is, it has a stronger attraction for the shared bonding electrons than does hydrogen. Therefore, we find the shared electrons associated more with the oxygen than with hydrogen, displaced from a symmetrical cloud to one in which the shared electron distribution favours oxygen. This establishes a partial positive charge on the hydrogen and a partial negative charge on the oxygen. This idea of electronegativity can be applied to constituents of larger molecules to give insight into how molecules interact.