2) Element symbol: Ar
 

3) Number of electrons, protons, and neutrons: 18 electron, 18 proton, 22 neutrons
 

4) Atomic number: 18
 

5) Atomic mass: 39.948
 

6) Characteristics:

Argon is composed of monatomic molecules and is colorless and odorless.
 

7)

History:

Argon was discovered in 1894 by the British scientists Sir Willian Ramsay and Baron Rayleigh. They were led to this discovery by a discrepancy between the density of supposedly pure nitrogen, prepared from air, and actually pure nitrogen prepared from ammonium nitrate.

Three things made from the element:

- used in electric-arc technology

- used in gas lasers

- used in arc welding
 

8) Isotopes:

On Earth, naturally occurring argon is a mixture of three stable isotopes: argon-36 (0.34 percent), argon-38 (0.06 percent), and argon-40 (99.60 percent)
 

9) The outermost (valence) shell of argon has eight electrons, making it exceedingly stable and, thus, chemically inert. Argon atoms do not combine with one another; nor have they been observed to combine chemically with atoms of any other element. Argon atoms have been trapped mechanically in cagelike cavities among molecules of other substances, as in crystals of ice or the organic compound hydroquinone (called argon clathrates)
 

10) Argon melts at -189.3 °C (-308.2 °F) and boils at -185.86 °C (-302.55 °F).