Noble gases are a group of elements that are found in the periodic table. They are characterized by having full outer electron shells, making them unreactive and stable. The noble gases included in this crossword are ARGON (5 letters), RADON (5 letters), KRYPTON (7 letters), XENON (5 letters), HELIUM (6 letters) and NEON (4 letters). ARGON is the most abundant noble gas in the atmosphere, while RADON is a radioactive gas that is found in soil and rocks. KRYPTON is used in lighting and photography, while XENON is used in medical imaging and lasers. HELIUM is the second lightest element and is used in balloons and blimps, while NEON is used in signs and advertising.