Answer:Argon is unreactive because it has the maximum number of electrons in its outer shell. Noble gases are unreactive because they have the full complement of electrons in their outermost energy levels.
Argon is element 18 on the periodic table, which means that it has 18 proton in it's nucleus. Argon is in group 8 or 18 depending on your periodic table. Argon is a gas at standard temperature and pressure with a density of 1.784g/l
