High Pressure, Matter at Extreme States

Washington, DC— Although helium is the second most-abundant element (after hydrogen) in the universe, it doesn’t play well with others. It is a member of a family of seven elements called the noble gases, which are called that because of their chemical aloofness—they don’t easily form compounds with other elements. Helium, widely believed to be the most inert element, has no stable compounds under normal conditions.