Name       : Argon
Symbol     : Ar
Atomic #   : 18
Atom weight: 39.948
Melting P. : -189.2
Boiling P. : -185.7
Oxidation  : 0
Pronounced : AR-gon
From       : Greek argos, "inactive"
Identified : Henry Cavendish in 1785
Appearance : Colorless, tasteless, odorless noble gas
Note       : Comprises about 1% of earth's atmosphere.

[Properties]

  Argon is a member of the Group-0 elements. Until the late 1960s, this
group was often called the inert gasses because it was believed that they
could not possibly combine with any other element to form compounds. Today
we know that the so-called inert gasses can indeed combine with other
elements. Admittedly, it is difficult to create these compounds; most of
them are highly unstable and some barely qualify as being compounds at all.
None of them has any practical application. In the world of theoretical
chemistry where truth and knowledge are more important than an improved
shoe polish, the notion that the noble gasses can combine with other 
elements is one of the most satisfying discoveries of this generation.
  Finding that the inert gasses are no longer inert has forced some changes
in chemical nomenclature. First, these are now NOBLE gasses instead of
inert gasses. This has not been a difficult change in nomenclature because
the terms were used interchangeably before inert fell from grace. Changing
the notation on most periodic tables is taking a bit longer, though. Notice,
for example, that the noble gasses on most periodic tables are still 
designated to Group-0. These were formerly known as the Group-O gasses
because of their unique oxidation state of zero. This is still the most
stable oxidation state for noble gasses, but we now know that others exist.
Some newer periodic charts call this group VIIA instead of 0.