Hg 2+ is also found in organic (carbon based) substances like dimethylmercury (Me 2Hg), which is far more toxic than inorganic forms of mercury and bioaccumulates in the tissues of living organisms. The mercuric cation is more stable and is generally associated with inorganic molecules, such as sulfur (in the mineral cinnabar), chlorine (mercuric chloride), oxygen and hydroxyl ions.
Mercury is also found in two positively charged, or cationic, states, Hg 2+ (mercuric) and Hg 1+(mercurous). Elemental mercury (Hg 0) has no electric charge. In nature, mercury has 3 possible conditions of electrical charge, or valence states. The metal is a fair conductor of electricity, but a poor conductor of heat. Mercury has a relatively high vapour pressure and the highest volatility of any metal, vapourizing to become a colourless, odourless gas. Fortunately, mercury does not form amalgam with iron, which allows for the element to be shipped in standard iron flasks containing 76 pounds, or 34.5 kilograms, of liquid mercury.
The element also combines with other metals such as tin, copper, gold and silver to form mercury alloys known as amalgams. The liquid is highly mobile and droplets combine easily due to low viscosity. Droplets of liquid mercury are shiny and silver-white with a high surface tension, appearing rounded when on flat surfaces. Mercury has a melting point of -38.9 oC, a boiling point of 356.7 oC, and is the only metal to remain in liquid form at room temperature.
The element's atomic mass is 200.59 grams per mole and its specific gravity is 13.5 times that of water. Like cadmium, zinc and lead, mercury is a naturally occurring element known as a "heavy metal" and can be toxic to living organisms.
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