Mercury is the only metal found in a liquid state at room temperature. Moreover, along with water, it is one of the few liquids found naturally on the Earth's surface. Pure mercury forms around volcanoes where heat separates it from its minerals, such as cinnabar, (mercury sulfide, HgS). This red mineral has been used for many centuries: the ancient Romans roasted cinnabar to release a liquid which they called hydrargyrus, meaning "silver water", alluding to the mercury obtained. It was later known as mercury because of how fast it flowed as a liquid stream. This metal is very poisonous: it can damage organs and nerves if inhaled or ingested. As a result, the use of this metal is carefully monitored. Mercury is used in some batteries, some thermometers and in low-energy compact fluorescent light bulbs (CFLs). Its compounds are used to prepare strong red paints. Until the early 18th century, mercury was used in tablets to treat some common ailments. It was gradually discontinued when its toxicity was discovered. Early precision barometers also contained this liquid, but they are rarely used today.

Summary of properties (Hg)

Atomic weight200.592(3)
Discoverer (year)unknown (ancient times)
Natural formliquid
Electron configuration[Xe] 414 5d10 6s2
Melting point (ºC)-39
Boiling point (ºC)357
Abundance in earth's crust (ppm)0.085
Isotope (abundance)196Hg (0.155), 198Hg (10.038), 199Hg (16.938), 200Hg (23.138), 201Hg (13.170), 202Hg (29.743), 204Hg (6.818()
Density g/cm313.55
Van der Waals radius (pm)223
Covalent radius (pm)132
Electronegativity (Pauling)2
Vaporization enthalpy (kJ/mol)59.11
Enthalpy of fusion (kJ/mol)2.29
Specific heat capacity (J/g·K) at 25ºC and 1 atm0.14
Thermal conductivity (W/cm·K) at 25ºC and 1 atm0.080
Oxidation state+2, +1
Electron affinity (eV)unstable ion
1st Ionization potential (eV)10.4375

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