Question: Who made 19th century advances in valence bonding?
About the article "Chemistry", section "Chemistry as science".

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The concept of covalence was developed in the middle of the nineteenth century in an attempt to rationalize the formulae of different chemical compounds.
In 1919, Irving Langmuir, borrowed the term to explain Gilbert N. Lewis's cubical atom model by stating that "the number of pairs of electrons which any given atom shares with the adjacent atoms is called the "covalence" of that atom."
The prefix "co-" means "together", so that a co-valent bond means that the atoms share valence.
Hence, if an atom, for example, had a +1 valence, meaning it has one valence electron beyond the complete shell, and another a −1 valence, meaning it requires one electron to complete its outer shell (missing an electron) , then a bond between these two atoms would result because they would be complementing or sharing their out of balance valence tendencies.
Subsequent to this, it is now more common to speak of covalent bonds rather than "valence", which has fallen out of use in higher level work with the advances in the theory of chemical bonding, but is still widely used in elementary studies where it provides a heuristic introduction to the subject. 
Walter Heinrich Heitler (; 2 January 1904 – 15 November 1981) was a German physicist who made contributions to quantum electrodynamics and quantum field theory.
He brought chemistry under quantum mechanics through his theory of valence bonding. 
 as science.
Under the influence of the new empirical methods propounded by Sir Francis Bacon and others, a group of chemists at Oxford, Robert Boyle, Robert Hooke and John Mayow began to reshape the old alchemical traditions into a scientific discipline.
Boyle in particular is regarded as the founding father of chemistry due to his most important work, the classic chemistry text "The Sceptical Chymist" where the differentiation is made between the claims of alchemy and the empirical scientific discoveries of the new chemistry.
He formulated Boyle's law, rejected the classical "four elements" and proposed a mechanistic alternative of atoms and chemical reactions that could be subject to rigorous experiment.
The theory of phlogiston (a substance at the root of all combustion) was propounded by the German Georg Ernst Stahl in the early 18th century and was only overturned by the end of the century by the French chemist Antoine Lavoisier, the chemical analogue of Newton in physics; who did more than any other to establish the new science on proper theoretical footing, by elucidating the principle of conservation of mass and developing a new system of chemical nomenclature used to this day.
Prior to his work, though, many important discoveries had been made, specifically relating to the nature of 'air' which was discovered to be composed of many different gases.
The Scottish chemist Joseph Black (the first experimental chemist) and the Dutchman J.
B. van Helmont discovered carbon dioxide, or what Black called 'fixed air' in 1754; Henry Cavendish discovered hydrogen and elucidated its properties and Joseph Priestley and, independently, Carl Wilhelm Scheele isolated pure oxygen.
English scientist John Dalton proposed the modern theory of atoms; that all substances are composed of indivisible 'atoms' of matter and that different atoms have varying atomic weights.
The development of the electrochemical theory of chemical combinations occurred in the early 19th century as the result of the work of two scientists in particular, J. J. Berzelius and Humphry Davy, made possible by the prior invention of the voltaic pile by Alessandro Volta.
Davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current.
British William Prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen.
J.
A. R. Newlands devised an early table of elements, which was then developed into the modern periodic table of elements by the German Julius Lothar Meyer and the Russian Dmitri Mendeleev in the 1860s.
The inert gases, later called the noble gases were discovered by William Ramsay in collaboration with Lord Rayleigh at the end of the century, thereby filling in the basic structure of the table.
Organic chemistry was developed by Justus von Liebig and others, following Friedrich Wöhler's synthesis of urea which proved that living organisms were, in theory, reducible to chemistry.
Other crucial 19th century advances were; an understanding of valence bonding (Edward Frankland in 1852) and the application of thermodynamics to chemistry (J. W. Gibbs and Svante Arrhenius in the 1870s).
Resonant bonding.
Hypervalent bonding.
In hypervalent molecules, there exists bonds which have significant non-bonding ionic quality to them.
This manifests as non-bonding orbital levels in molecular orbital theory, while in valence bond theory it is analyzed as a form of resonant bonding. 
Isaac Newton has been credited with the first description of conformal interaction observed through the interference phenomenon known as Newton's rings, though it was S. D. Poisson in 1823 who first described the optical characteristics of two identical surfaces in contact.
It was not until the 19th century that objects were made of such precision that the binding phenomenon was observed.
The clinging together was described as "wringing together", or as "ansprengen" in German.
By 1900 optical contact bonding was being employed in the construction of optical prisms, and the following century saw further research into the phenomenon at the same time that ideas of inter-atom interactions were first being studied.