Argon is an inert gas in group VIII A of the periodic table with atomic number 18, an atomic weight of 39.948, and a density of 1.40 Mg/m 3. In the solid state it forms an fcc crystal with a melting ...

14. An 18-sided shape is called an octadecagon or an octakaidecagon. 15. 18 is the atomic number for the noble gas argon. 16. Argon and the other noble gases appear in the last column, or group ...