What does it mean when atoms are sticking to each other ?
Emil Fischer developed the Fischer projection technique for viewing 3 - D molecules on a 2 - D sheet of paper:In 1898 , Ludwig Boltzmann , in his " Lectures on Gas Theory " , used the theory of valence to explain the phenomenon of gas phase molecular dissociation , and in doing so drew one of the first rudimentary yet detailed atomic orbital overlap drawings .