Non-Metals in Water
A non-metal does not react with water but it is usually very reactive in air, which is why some of them are stored in water.
For example, one of the highly reactive non-metals is phosphorus. It catches fire when exposed to air that is why it is stored in water to prevent its contact with atmospheric oxygen.
Under normal conditions of temperature and pressure, some non-metals are found as gases, some found as solids and one is found as liquid.
In contrast, except mercury, all metals are solids at room temperature. The fact that so many non-metals exist as liquids or gases means that non-metals generally have relatively low melting and boiling points under normal atmospheric conditions.
Non-metals are the elements which form negative ions by accepting or gaining electrons. Non-metals usually have 4, 5, 6 or 7 electrons in their outermost shell.