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Greatest Discoveries of Chemistry

Pioneering discoveries that became turning points in the history of
chemistry.

Oxygen (1770s)

British educator and philosopher Joseph Priestley (1733 – 1804)
discovered oxygen in experiments, isolated the gas, and described its
function in combustion and respiration. He also invented soda or
carbonated water by dissolving fixed air with water. Unaware of the
significance of his discoveries and because of his stubborn refusal to
abandon the phlogiston theory, he named the new gas “dephlogisticated
air.” However, it would be the French chemist Antoine Lavoisier (1743 –
1794) who gave the gas its present name, and was able to explain the
nature of the element, accurately describing its role in combustion that
totally discredit the phlogiston theory. In addition, Lavoisier
collaborated with others to develop a systematic chemical nomenclature
that facilitates dialogue among chemists and is still very much in use
today.

Atomic Theory (1800s)

John Dalton (1766 – 1844), English chemist and physicist, proposed the
atomic theory, which states that: a.) all elements are made up of tiny
particles called atoms; b.) all atoms of an element are identical; c.)
the atoms of dissimilar elements can be distinguished from one another
by their corresponding relative weights; d.) atoms of an element can be
combined with atoms of another elements to form chemical compounds; and
e.) atoms cannot be created, broken down into smaller particles, nor
destroyed in a chemical process. He also presented a way of associating
invisible atoms with quantifiable amounts such as mass of a mineral or
volume of a gas. Dalton’s theory has undergone modifications through the
centuries, but it has as much significance for the future of the science
as Lavoisier’s oxygen-based chemistry had been.

Molecules are Made Up of Atoms (1810s – )

At a time when the words “atom” and “molecule” were used
interchangeably, Italian scientist Amedeo Avogadro (1776 – 1856)
clarified that atoms combine to form molecules; and proposed his
eponymous principle which asserts that “Equal volumes of ideal gases, at
the same conditions of temperature and pressure, contain equal numbers
of particles or molecules.”

The Electron (1890s)

Through a series of experiments using cathode ray tubes, J. J. Thomson
(1856 – 1940) discovered that cathode rays emitted negative charged
particles, a component that makes up atoms. He called these particles
“corpuscles,” now known as electrons. He proposed that plum pudding
model, in the belief that atoms consisted of an abundance of these
corpuscles teeming in an ocean of positive charged particles; but this
was subsequently proven to be erroneous when Ernest Rutherford (1871 –
1937) developed the orbital theory of the atom and discovered through
his famous gold foil experiment that atomic masses are largely
concentrated in the nucleus surrounded by electrons.

Electrons for Chemical Bonds (1910s – )

On the foundation of Ernest Rutherford’s theories, Danish physicist
Niels Bohr (1885 – 1962) published his atomic structure model,
postulating that electrons move in specific orbits around the nucleus;
and that the chemical properties of an element are largely dependent of
the number of electrons in the outer orbit. These discoveries led the
way to a greater understanding of the physical interactions between
atoms and molecules, a process called chemical bonding.

Periodic Table of the Elements (1860s – 1870s)

Russian chemist and inventor Dmitri Mendeleev (1834 – 1907) discovered
that if he tabulize the sixty-three known elements in order of
increasing atomic number, their chemical properties recur in periodic
cycles. So he devised the periodic table of the elements that
successfully predicted the existence of yet undiscovered elements. In
fact, three were found in his lifetime: scandium, germanium and gallium.
The design of the table has been refined and expanded as new elements
are discovered, making it absolutely essential to the academic
discipline of chemistry, and at the same time, supplying a very valuable
tool in classifying, systematizing and studying different chemical
behaviors.

Urea Synthesis (1820s)

Friedrich Woehler (1800 – 1882), German physician and chemist,
accidentally synthesized an organic substance, urea, from inorganic
matter; and as a result, unintentionally overthrew vitalism, the belief
that chemicals released by living organisms are essentially different
from non-living things. His discovery started the new subfield of
organic chemistry.

Chemical Structure (1850s)

Following years of researching carbon-carbon bonds, German organic
chemist Friedrich Kekule (1829 – 1896) suggested that the chemical
structure of benzene as a ring-shaped arrangement of six carbon atoms
after having dreamt of a snake grasping its own tail. The structure
explained the difficulty why carbon atoms have the ability to bond up to
four atoms simultaneously, a property known as tetravalence. Kekule,
with the breakthrough of his theory of chemical structure, led to a
greater understanding of molecular structure and resulted in the
explosive development of the field of organic chemistry.

Electrolysis (1800s)

Having discovered that electricity can alter chemicals, British inventor
Humphry Davy (1778 – 1829) pioneered the use of electrolysis as a method
for splitting up chemical compounds into their constituent parts by
passing an electric current through them. With numerous batteries used
in electrolysis, he discovered several new elements: potassium, sodium,
strontium, boron, magnesium and barium.

Atoms Have Signatures of Light (1850s)

German physicist Gustav Kirchhoff (1824 – 1887) and chemist Robert
Bunsen (1811 – 1899) worked together in a field called spectrum analysis
and learned that every element either absorbs or releases light at
discrete wavelengths, producing discrete spectral lines. Though
Kirchhoff and Bunsen did not understand about the existence of energy on
the atomic level, the existence of spectral lines was satisfactorily
explained by the Bohr’s atomic model, leading to the development of a
completely new field called quantum mechanics.

Radioactivity (1890s – 1900s)

Marie (1867 – 1934) and Pierre Curie (1859 – 1906) were able to extract
uranium from pitchblende, and noted that the pitchblende seem to be more
active than what they had extracted. They deduced that the ore, aside
from uranium, contain traces of an unknown substance or element that are
radioactive. Their study led to the discovery of new elements, which
they dubbed as polonium and radium.

Plastics (1860s, 1900s)

In 1869, American inventor John Wesley Hyatt (1837 – 1920) was able to
develop a commercially viable way of producing celluloid plastic in his
effort to find an ivory substitute for manufacturing billiard balls.
Celluloid became the first synthetic plastic and was utilized as a
replacement for more expensive materials as ivory, amber and
tortoiseshell. By the first decade of the twentieth century,
Belgian-born American chemist Leo Baekeland (1863 – 1944) invented the
first hard moldable plastic called Bakelite, a synthetic substitute
characterized by insulating and heat-resistant properties. Soon it
permeated almost every branch of industry, and became a ubiquitous
presence in nearly every object in society. However, the use of plastics
has raised serious environmental concerns in the last few decades.

Fullerenes (1980s)

Chemists Robert Curl (1933 – ), Harold Kroto (1936 – ) and Richard
Smalley (1943 – 2005) discovered a very stable although not necessarily
unreactive form of carbon with cage-like molecular structure. Other
carbon compounds of similar structure have also been discovered and are
collectively known as buckminsterfullerenes or fullerenes. The
structures are made up entirely of carbon molecules arranged in
spherical, ellipsoidal, tubular or ring-shaped form. The term was named
after Richard Buckminster Fuller (1895 – 1983), who was an architect
best known for creating geodesic-domed structures in the mid-twentieth
century, which are sometimes referred as buckyballs.

References

1. Greatest Discoveries in the Field of Chemistry. SCIENCERAY
HYPERLINK
«http://scienceray.com/chemistry/greatest-discoveries-in-the-field-of-ch
emistry/»
http://scienceray.com/chemistry/greatest-discoveries-in-the-field-of-che
mistry/

2. Chemistry. From Wikipedia, the free encyclopedia.
http://en.wikipedia.org/wiki/Chemistry

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