Modern Chemistry Lavoisier's results and Atomic Theory
provided chemists their first in depth understanding related to
the nature of chemical reactions. Another cornerstone which
dealt with the inherent property of all matter came a few years
later in the form of atomic theory advanced in 1805 by an
English schoolteacher, John Dalton. This theory puts forward
the theory that matter constitutes of small particles which are
named atoms and that chemical changes take place between
atoms or groups of atoms. Finally, being equipped with in
depth views about the nature of matter and of chemical
reactions, chemistry began making rapid strides.
Very soon one after the other the gas laws of Joseph Louis
Gay-Lussac and that of Joseph Louis Proust's law of definite
proportions came into being. In this period too came the
hypothesis of Amedeo Avogadro, an Italian chemist, about the
number of molecules in a volume of gas. To Dalton's theory
that the atoms of a single element have the same weight,
Avogadro, in 1811, added the idea that one quart (or other
volume) of a gas has the number of molecules which are
exactly same as that of any other gas with an equal volume if
both are allowed to rest at the same temperature and pressure.
His calculations also showed that if the gas is an element, such
as hydrogen or oxygen, the atoms usually unite in pairs to
form molecules (written H2, O2, and so on). The scientists
knew, however, that equal volumes of different gases have
unequal weights. Avogadro's hypothesis implied that this showed
relative weights of single atoms. This has been proved to be
correct, and today Avogadro's law may be stated thus: equal
volumes of all gases under the same conditions of temperature
and pressure contain the same number of molecules. Humphry
Davy, about 1806, isolated a number of elements to add to the
growing list.
Jons Jakob Berzelius, in 1826, analyzed hundred of compounds
and published accurate tables of atomic weights. Friedrich
Wohler's synthesis of urea in 1828 proved that organic
compounds could be made in the laboratory and opened a
vast new field of chemistry. This began the development of the
concept that organic compounds have geometric structure.
Friedrich Kekule proposed cyclic (ring) structure of benzene
about this time. Michael Faraday, formulated the laws of
electrochemistry in 1834.
