Did You Know?► The discovery of mercury was made thousands of years ago, and traces of the element can even be found in Egyptian tombs that date back to the year 1500 B.C.
* Caution: Mercury is an extremely hazardous substance and can be fatal if ingested. Hence, it should be kept out of reach of children and pets. Also, under no circumstances should the metal be handled with bare hands.
Mercury is a unique metal and anyone who sees mercury for the first time cannot help being fascinated by its incredible nature. In ancient times, mercury was known as 'quicksilver', which roughly implied that the silver was alive. The origins of this name can be based on the fact that when liquid mercury is poured on a flat surface, it forms distinct small beads that move around as if they are alive. Antoine Lavoisier, a French chemist, was the one who distinguished mercury as an element.
►► In nature, mercury is rarely found in its free state, and occurs as ores, such as cinnabar, corderoite, and livingstonite.
►► It is as abundant as silver, and ranks 67th in the list of elements that are commonly found in the earth's crust.
►► Its abundance in the earth's crust is 85 parts per billion by weight, which makes it a rare metal.
►► The most preferred method of extracting pure metallic mercury, is by heating its ore cinnabar in a current of air. This process releases vapors of mercury, which are then condensed to obtain the pure metal. Here is the equation for the process.
HgS + O2 ➔ Hg + SO2
►► There are around 34 known isotopes of the metal, and their mass numbers range from 175 to 208. However, only 7 of them occur in nature, and 202Hg is the most abundant.
Here are some facts about the physical properties of mercury.
►► Mercury is a silvery-white metal, with a shining appearance. It is highly reflective, and moves at the slightest touch.
►► The unique physical properties of the element is a result of the two electrons in its outermost shell. Also known as valency electrons, they form loose bonds between adjacent atoms of the metal, and are responsible for conduction of electricity.
►► It is a poor conductor of heat, but is a fairly good conductor of electricity.
►► It has a very high coefficient of expansion.
►► When cooled to temperatures close to absolute zero, mercury acquires properties of a superconductor.
►► The boiling point of mercury is 357 degrees centigrade, which means the metal exists as a gas above this temperature.
►► It has a very high specific gravity, which means it is many times heavier than an equal volume of water. In fact, it is so dense that even a block of lead can float in it!
►► An interesting thing about mercury is that even though it is a liquid at room temperature, it is not wet. In other words, it does not get absorbed by substances, unlike liquids do. This is due to its negative co-efficient of surface tension. Also, it has a convex meniscus, which is exactly the opposite of that of most other liquids.
►► When pure mercury is spilled on a surface, it forms several small droplets that are spherical in shape. These spherical beads of the metal can easily pass through small cracks on the surface, or get strongly attached to some substances. Hence, it is difficult to remove them completely.
►► One of the distinct physical properties of mercury is its high surface tension. It is also characterized by low viscosity, which makes it highly mobile.
►► The vapor pressure of mercury is relatively high, and it is highly volatile.
►► The triple point of mercury is -38.8344 °C. It is the temperature at which the three phases of a substance (solid, liquid, and gas) coexist in thermodynamic equilibrium.
|Number of protons/electrons||80|
|Number of neutrons||121|
|Atomic mass||200.59 amu|
|Density @ 293 K||13.456 g/cm3|
|Number of energy levels||6|
|Atomic radius||157 per molecule|
|Atomic volume||14.8 cm3/molecule|
Given below are the facts on the chemical properties of mercury.
►► It reacts with atmospheric oxygen, in the presence of moisture, to form a gray oxide.
►► It reacts with chlorine and sulfur, to form compounds such as mercuric chloride, mercurous chloride, mercuric sulfide, etc.
►► Vapors of mercury react with noble gases, namely neon, argon, krypton, and xenon, in the presence of electrical discharge, to form products that are held together by van der Waals' forces.
►► A unique property of mercury is that it forms stronger bonds with atoms of other elements, than it does with its own atoms. Thus, it readily reacts with different metals to form alloys, which are known as amalgams. The atoms in an amalgam are linked together by metallic bonds. This property of mercury finds use in metallurgy, dentistry, and manufacturing of chemicals. However, there are some metals, such as iron and platinum, that do not react with mercury to form amalgams.
►► Mercury occurs in nature in 3 valence states. While the pure element has no charge and is neutral, it exhibits two positively charged states in its compounds, which are Hg2+(mercuric) and Hg1+ (mercurous). The higher valency state of mercury is found in inorganic compounds, such as mercuric chloride, mercuric sulfide, etc. The lower valency, on the other hand, occurs mostly in organic compounds.
Wondering what are the uses of mercury? Well, here they are...
►► One of the primary uses of mercury is in mining, where it is used to recover metallic gold or silver from their ores. In this process, the ores are finely crushed, and the particles are heated in vessels of iron or stone, that contain mercury. The mercury amalgamates with the gold and silver grains present in the ore, and the amalgams are then allowed to solidify. The last step in the process is the heating of the amalgams in a retort to release vapors of mercury, which is then liquefied to be used again. Once the mercury is driven off, what is left in the retort is pure gold or silver.
►► Mercury is used in a host of scientific and medical instruments, such as the barometer, thermometer, diffusion pump, hygrometer, hydrometer, sphygmomanometer, and esophageal dilators.
►► Mercury is used in neon signs for advertising.
►► Silver amalgams (alloys of silver and mercury) are used in dental fillings.
►► Here are some other uses of the metal.
- Manufacturing pesticides
- Use of mercury cells as electrodes in the synthesis of chlorine and sodium hydroxide
- Manufacturing paints
- Manufacturing batteries
- Manufacturing chemical pesticides
- As a catalyst in chemical reactions
- Mercuric chloride (HgCl2) has antiseptic properties. It is also used in insecticides and rat poison.
- Mercurous chloride (Hg2Cl2) is also known to possess antiseptic properties.
- Mercuric sulfide (HgS) is used to make vermilion, a reddish-orange pigment.
- Mercuric oxide is used in ointments for skin infections.
- Mercuric sulfate (HgSO4) is used as a catalyst in chemical reactions.
- Mercuric fulminate [Hg(CNO)2] is used as a detonator to trigger explosives.
►► It is a poisonous metal, and the vapors of mercury are readily absorbed into the body through the respiratory tract, the digestive tract, and the skin. Hence, it is essential to remove every trace of spilled mercury, because it gets evaporated at room temperature.
►► The hazard associated with the metal makes it essential that one exercises extreme caution while handling it. It should be stored in secure and airtight containers that prevent the vapors from escaping. Also, one should avoid heating the metal indoors.
►► Mercury, in its liquid state, can be held in the hand. However, doing so with bare unprotected hands is not advisable, because it can seep through the skin.
►► Weird as it may seem, but the major cause of mercury poisoning in humans is the consumption of fish that contain very high levels of methylmercury, a highly toxic bioaccumulative substance that accumulates within living organisms.
➊ Mercury is the only metal which is still known by its alchemical planetary name. Not only this, even the ancient planetary symbol (☿) is used even today to represent the element.
➋ The triple point of mercury is a fixed point on the International Temperature Scale.
➌ If you're wondering why the chemical symbol for mercury is Hg, it's only because of the Latin name for the metal which is hydrargyrum.
➍ The atomic number of mercury is 80, while that of gold is 79. This means that mercury sits right next to gold on the periodic table of elements!
➎ Mercury is 13.6 times heavier than water!
➏ Even as early as the time of Christ, alchemists were successful in obtaining mercury from its ore, and in creating amalgams!
➐ Interestingly, mercuric oxide (HgO) played a "key role" in the discovery of oxygen. Both Carl Wilhelm Scheele and Joseph Priestley, who are both credited with the discovery of oxygen, discovered the gas by heating mercuric oxide (HgO).
➑ Since the freezing point of mercury is -38.83 degrees Celsius, instruments containing the metal are rendered useless in the Arctic and Antarctic regions, where the lowest recorded temperature is around -70 °C.