Oxygen
...Oxygen in the biosphere is essential in the processes of
respiration and metabolism, the means by which animals derive the energy needed
to sustain life. Furthermore, oxygen is the most abundant element at the surface
of the Earth. In combined form it is found in ores, earths, rocks, and gemstones,
as well as in all living organisms. Oxygen is a gaseous chemical element in
Group VA of the periodic table. The chemical symbol for atomic oxygen is O, its
atomic number is 8, and its atomic weight is 15.9994. Elemental oxygen is known
principally in the gaseous form as the diatomic molecule, which makes up 20.95%
of the volume of dry air. Diatomic oxygen is colorless, odorless, and tasteless.
Two 18th-century scientists share the credit for first isolating elemental
oxygen: Joseph PRIESTLEY (1733-1804), an English clergyman who was employed as a
literary companion to Lord Shelburne at the time of his most significant
experimental work, and Carl Wilhelm SCHEELE (1742-86), a Swedish pharmacist and
chemist. It is generally believed that Scheele was the first to isolate oxygen,
but that Priestley, who independently achieved the isolation of oxygen somewhat
later, was the first to publicly announce his findings. The interpretation of
the findings of Priestley and the resultant clarification of the nature of
oxygen as an element was accomplished by the French scientist Antoine-Laurent
LAVOISIER (1743-94). Lavoisier's experimental work, which extended and improved
upon Priestley's experiments, was principally responsible for the understanding
of COMBUSTION and the establishment of the law of conservation of matter.
Lavoisier gave oxygen its name, which is derived from two Greek words that mean
"acid former." Lavoisier held the mistaken idea that oxides, when dissolved in
water, would form only acids. It is true that some oxides when dissolved in
water do form acids; for...
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