Development of Bonding Models Based on the Periodic Table

Kossel and Lewis' description of the chemical bonding in ionic and covalent compounds in 1916 made an important contribution, which connected the Periodic Table to modern valence theory. In a 1919 paper Langmuir made the perceptive observation that neutral molecules, which had the same number of electrons, e.g. N₂ and CO and N₂O and CO₂, had remarkably similar physico-chemical properties. Inorganic chemists have used this isoelectronic principle to interconnect a wide range of compounds and thereby explore the implications of the Periodic Table.