Chemical Bond

Some of the most vigorous speculation about chemical bonding took place in the young field of organic chemistry. In trying to understand the structure of organic compounds, for example, Friedrich Kekulé suggested that the carbon atom is tetravalent; that is, it can bond to four other atoms. He also hypothesized that carbon atoms could bond with each other almost endlessly in long chains.

Kekulé had no very clear notion as to how atoms bond to each other, but he did develop an elaborate system for showing how those bonds might be arranged in space. That system was too cumbersome for everyday use by chemists, however, and it was quickly replaced by another system suggested earlier by the Scottish chemist Archibald Scott Couper. Couper proposed that the bond between two atoms (what the real physical nature of that bond might be) be represented by a short dashed line. Thus, a molecule of water could be represented by the structural formula: H-O-H.

That system is still in existence today. The arrangement of atoms in a molecule is represented by the symbols of the elements present joined by dashed lines that show how the atoms of those elements are bonded to each other. Thus, the term chemical bond refers not only to the force of attraction between two particles, but also to the dashed line used in the structural formula for that substance.