Mechanical bonding can easily be understood by looking at a screw attached to a piece of wood. In this case. there are no chemical bonds that form between the screw and the wood, and the screw is purely mechanically retained. Chemical bonding would occur if atomic groups present in the wood would interact with atomic groups present in the surface of the screw.
From the above we can conclude that chemical bonding requires atomic interactions. Such interactions can be studied by use of different spectroscopic analyses capable of detecting energy changes in the outer electron orbits of the interacting materials. Such energy changes indicate chemical bond formation.