Inert
（重定向自Inertness）
In English, to be inert is to be in a state of doing little or nothing.
In chemistry, the term inert is used to describe a substance that is not chemically reactive.
The noble gases were previously known as inert gases because of their perceived lack of participation in any chemical reactions. The reason for this is that their outmost electron shells (valence shells) are completely filled, so that they have little tendency to acquire or lose electrons. It is now known that most of these gases in fact do react to form chemical compounds, such as xenon tetrafluoride. Hence, they have been renamed to noble gases. However, a large amount of energy is required to drive such reactions, usually in the form of heat, pressure, or radiation, often assisted by catalysts. The resulting compounds often need to be kept in moisture-free conditions at low temperatures to prevent rapid decomposition back into their elements.