Sir Edward Frankland was a British chemist, one of the foremost English chemists of his
day. He laid the foundation of modern structural chemistry through his
discovery of the theory of valence, which states that atoms come
together to make chemical compounds in regular ratios. Frankland was one of the originators of organometallic chemistry and introduced the concept of combining power or valence.
An expert in water quality and analysis, he was a member of the second
royal commission on the pollution of rivers, and studied London's water
quality for decades. He also studied luminous flames and the effects of atmospheric pressure on dense ignited gas, and was one of the discoverers of helium.
He also introduced the term “bond” to describe the way that atoms
link to each other. Frankland became professor of chemistry at the
prestigious Royal College of Chemistry and he published Water Analysis for Sanitary Purposes.
Edward Frankland was born in Lancashire, England on January 18, 1825,
an illegitimate son of a prominent lawyer. At the age of 15, he became an
apprentice in a chemist’s shop. By 1847, he was a chemistry teacher at
Queenwood College, Hampshire, but soon went to Germany in Marburg to
work with Robert Bunsen for three months.
Frankland Discovers Organometallic Compounds
While working with Bunsen, Frankland became fascinated by a class of
chemicals that bound metal atoms to other compounds, now called
organometals. The particular set of these that he was looking at were
zinc dialkyls.
An addition to studying organometals, he used these compounds for
entertainment. He described the process of adding water to these
compounds, which resulted in a greenish blue flame, several feet long,
shooting out of the tube. The display caused excitement among those
present and it diffused an abominable odor.
This pattern, however, had actually been seen before. A few years earlier, Alexander Crum Brown reported it in his M.D. thesis at the University of Edinburgh, entitled “On the Theory of Chemical Combination.”
A General Symmetry of Chemical Compounds Formula
What both Crum Brown and Frankland saw was that when elements
combine, they did so in whole number ratios. Antoine Lavoisier had been
moving to the idea when he split and recombined water, and found
constant proportions of hydrogen and oxygen were always involved.
Frankland took this further and developed what he called atomicity, now
known in the chemistry as valence. In his first report he said, “The
combining power of the attracting element… is always satisfied by the
same number of atoms…”
Frankland’s Valence Theory
The theory of valence states the following:
The valence number equals the number of chemical bonds that any given atom can make with other atoms when forming a compound.
In terms of atomic bonding, the idea is that every atom has a fixed
number of bonds that it can form, and that to be stable, all of these
bonds must be used. For example, if a hydrogen atom bonds with another
hydrogen atom, then the bonds on each atom will be fully used in forming
H2, otherwise known as the molecule of hydrogen. Alternatively, two
hydrogen atoms can combine with the two bonds of oxygen to form H-0-H,
or water. Frankland further introduced the compound notation for what is
now known as H20 (water.)
Valence of Carbon Forming Organic Chemical Compounds
The concept of valence was picked up and developed later by Friedrich
August Kerkule, who decided that the valence of carbon must be four. He
further suggested a radical idea that this would allow carbon to form
into chains of atoms, therefore creating huge molecules. He was right.
In 1865, Kerkule proposed that carbon not only form chains but also
link into closed six-atom rings. In the simplest carbon molecule, three
of each carbon’s bond on each carbon binds to a hydrogen atom. The
resulting molecule is sweet smelling benzene, an organic chemical
compound, containing six atoms of carbon and six hydrogen atoms.
Scientific Legacy of Edward Frankland
Edward Frankland’s concept of the theory of valence forms the
foundation of modern structural chemistry. Kerkule’s later realization
that carbon can form chains and rings gave rise to organic chemistry.
Between them, Frankland and Kerkule enabled chemistry to become an
important tool in the creation of new complex compound molecules beyond
what already existed in their day.
The discovery of the theory of valences produced a huge impact in
chemical engineering and industrial purposes that range from medical
drugs to textile dyes. For instance, benzene has been used as an
additive in gasoline. It has also been used as a solvent and precursor
to industrial chemicals in drugs, plastics, dyes and synthetic rubber.
Sir Edward Frankland was knighted in 1897. After a brief illness, he
died two years later, in August 9, 1899.
Suggested Video:
Theory of Valence. YouTube, uploaded by Ruth Robinson. Accessed May 21, 2014.
Valence Bond Theory. A gentle introduction to the concept of valence bond theory, which treats a chemical bond as an overlap of atomic orbitals. YouTube, uploaded by Ben's Cham Videos. Accessed May 21, 2014.
Sources:
Farndon, John, etal. The Great Scientists. London: Arcturus Publishing. (2005)
McGovern, Una, Ed. Biographical Dictionary. Edinburgh: Chambers. (2002)
Moore, Pete. E=MC². London: Quintet Publishing Ltd. (2002)
Note: I originally published this piece for Suite101.com. This is an abridged version. / Tel
(c) May 2011. Tel. Inspired Pen Web. All rights reserved.
