Name       : Oxygen
Symbol     : O
Atomic #   : 8
Atom weight: 15.9994
Melting P. : -218.4
Boiling P. : -182.962
Oxidation  : -2
Pronounced : OK-si-jen
From       : Greek oxys + genes, "acid former"
Identified : Carl Wilhelm Scheele in 1772
Appearance : Colorless, odorless, tasteless gas; pale blue liquid
Note       : Vital for sustaining life

[Properties]

  Oxygen is usually described as a colorless, odorless, tasteless gas
that is essential to living organisms.  Given the proper conditions
for the reactions, oxygen reacts with virtually every known element
to produce oxides.
  Oxygen heads the Group-VIA elements on the periodic table.  The
other members of this oxygen group are sulfur (S), selenium (Se),
tellurium (Te), and polonium (Po).  All except polonium are relatively
plentiful in nature.
  There are two allotropes of oxygen, one composed of two oxygen
molecules and the other composed of three.  The latter is known as
ozone.  Ozone is a very strong oxidizing agent that is capable of adding
an oxygen molecule to stable ions, thus changing sulfides to sulfates,
dioxides to trioxides, and so on.  This property makes it useful as a
disinfectant and bleaching agent.  It is also used in the treatment of
sewage and the manufacture of chemicals.
  Ozone occurs naturally in the earth's upper atmosphere where it serves
as an effective shield against harmful radiation from the sun.
Commercial amounts are prepared by passing oxygen through an electric
spark.  The pungent odor often detected around electrical equipment is
often that of ozone.