We all have been studying chemical bonds, specifically covalent, told to us that it composes of electron sharing between participating atoms. But do we have a scientific evidence that somehow conforms or substantiates this theory? For example, We have evidence to 'believe' in electrons. The discovery of electron as a particle common to all elements, supports this. The discovery of electron, involving glowing tube, was a macroscopic one and maybe that is the reason it seems very convincing to 'believe' in the existence of electrons. But from where comes the idea that it is the electrons that participate in bonding? Do we have evidence that supports this?