MERCURY

Name: Mercury (named after the Roman god equivalent to Hermes in Greek mythology)

Symbol: Hg

Group: 12

Period: 6

Block: d

Category: Transition metals

Atomic number: 80

Atomic mass: 200.592 u

Electrons per shell: 2, 8, 18, 32, 18, 2

Electronegativity: 2

Density: 13.53 g/cc

Melting point: Molten at room temperature. Solidifies at -38.83°C

Boiling Point: 356.73°C

Thermal Conductivity: 8.3 W (m K)

Electrical Conductivity: 1 × 10^6 S/m

Magnetic Order: Diamagnetic

Ordinary State: Liquid

Oxidation States: +1, +2

Mohs Hardness: Irrelevant

Vickers Hardness: Irrelevant

Brinell Hardness: Irrelevant

Most Stable Isotopes: Hg-196 (0.15%), Hg-198 (10.04%), Hg-199 (16.94%), Hg-200 (23.14%), Hg-201 (13.17%), Hg-202 (29.74%), and Hg-204 (6.82%)

Discoverer: Known since ancient times

Mercury is one of the few elements known since Antiquity and is unique in its kind as a metal that appears in a liquid state under normal temperature and atmospheric pressure conditions.

It is considered one of the famous "seven metals" (along with Gold, Silver, Copper, Iron, Tin, and Lead) and, like Gold and Silver, has played a much more relevant role, for obvious reasons, in pseudo-scientific branches than in metallurgical ones. Its only use as a metal in metallurgy is for the extraction of Gold, a method that has been blocked in Europe, North America, and other parts of the world such as major Asian powers and the Arabian periphery, but which continues to be used in less developed (or developing) countries, being one of its primary uses.

Regarding Mercury, it is almost more interesting to explain why it is liquid instead of solid, weighs so much, and behaves as it does, because if we talked about its uses, there would be little to discuss: it has very specific applications that are increasingly being reduced due to the fact that it represents a danger to all known forms of life and is effectively treated as a toxic metal.

The history of this metal (and, therefore, its use) is not like any other on record: being liquid yet very dense (denser than Lead but less than Gold), relatively noble (almost as noble as Silver, a precious metal), and not normally altered under ordinary circumstances (it did not dissolve in water, nor oxidize or sulfidate easily), in several Asian cultures, medicinal properties were attributed to it (as an elixir, no less): it was consumed in pure form, like drinking a normal beverage, or mixed to improve the taste or simply to unknowingly enhance the potion.

You shouldn't mock the ignorance of these people; remember that it was a long time ago, and they were unaware that what they were doing not only had no beneficial effects but would actually end up killing them (or at the very least, if they were lucky enough to survive, falling into the grip of dementia).

The toxic nature of Mercury is known precisely through cases like these, although the magnitude of being able to say "enough is enough" varied greatly. That is to say, despite knowing it was dangerous, it continued to be used (and indeed, as I said before, it is still used) in applications that, while not necessarily "medical," involved direct contact with the metal, which is capable of filtering through the skin's mucous membranes.

For the Greeks (and contemporary neighboring cultures), Mercury was nothing but "Live Silver". When we say "live," we refer precisely to its liquid state, its ability, like water, to adopt the shape of its container, being truly amorphous.

Its property of "Live Silver" is precisely where its name derives: "Hydrargyros", although technically this translates as "Liquid Silver". In England and other "sister" countries, at least in the field of science, different names were used than the one we use, "Mercury," so as not to confuse it with the planet of the same name or the Roman god (who in turn derives from Hermes). The unofficial Anglo-Saxon name for the element is "Quicksilver" (it has nothing to do with the clothing brand), and as you can see, it is a combination of "Quick" (fast, fleeting, agile) + "Silver". It is called one way or another depending on the language.

The characteristic that separates Mercury from the rest of the more or less known metals is none other than the fact that it is liquid at ambient temperature and pressure. Later, I will explain in the simplest and most enjoyable way possible why it is liquid and not solid, like most metals.

Although for a long time Mercury was considered the only liquid element, Gallium melts at approximately 29ºC. Therefore, for anyone living in a tropical or simply warm enough environment, it can be justified that not only Mercury, but also Gallium, are two metals that can be considered liquid at "room temperature". It should be clarified that when "room temperature" is mentioned, a range from 1 to 25ºC (usually) is considered, with a pressure of 1 ATM. If we were even more precise, we could say that Cesium and Rubidium (two alkali metals) also fall into this category, but they are so reactive that you will only be able to see them in their pure state in small vacuum-sealed glass ampoules (capsules) or filled with an inert gas, usually Argon.

Gallium solidifies below 29ºC (the purity of the metal also plays a role), but it is not as popular as Mercury, nor does this chapter correspond to this p-block metal.

Mercury is very dense compared to metals known since ancient times (denser than Lead but less dense than Gold), quite noble, not very reactive, a classic chalcophile (found in combinations with Sulfur). The main ore of Mercury is Cinnabar, and the world's largest mines are in Spain. Extracting the metal is complex, not because it reacts and becomes contaminated, but because when trying to reduce Cinnabar (or any other Mercury mineral), it is released as a vapor that must be "trapped" with appropriate instrumentation, usually an inverted glass vessel, connected by another glass tube to where the reaction takes place. The Sulfur is released as Dioxide (very polluting and poisonous, by the way) while the gaseous Mercury condenses after a while until it is collected and stored. Once purified, Mercury is kept in dry and humid air, and is insoluble in fresh and salt water, but if it is spilled or lost, it is irrecoverable.

Logically, there are no mechanical data for solid Mercury, although it is known to be ductile and malleable, and can be cut with a table knife. This should not be surprising given that it is part of Group 12 of the Periodic Table and shares some characteristics with Cadmium.

Mercury is a heavy metal, and in its case, although it also serves to say that it is very dense, we mean that it is toxic. Cadmium, Bismuth, Arsenic (depending on the author), Lead, Thallium, and Mercury itself form this group of the Periodic Table of Elements, famous from a negative point of view due to their toxicity. The least dangerous is Bismuth (to such an extent that comparing it with Lead and Mercury seems almost unfair), but Lead, Cadmium, and Mercury are particularly dangerous as they replace trace element atoms (like Iron or Carbon) given that they share some characteristics with them (Lead, for example, has the same oxidation states as Carbon and is in fact a member of the same group); something similar happens with Mercury.

Mercury (Hg), a chemical element with atomic number 80, is a group 12 transition metal, notable for being liquid at ambient temperature and pressure (0–25 °C, 1 atm), with a density of 13.53 g/cm³ and an abundance of 0.08 ppm in the Earth's crust. Its corrosion resistance is outstanding among metals, classifying it as relatively noble, although its liquid state makes it a unique case, as it acts as a corrosive agent by forming amalgams with other metals. Primarily extracted from cinnabar (HgS) through thermal reduction (600 °C), mercury condenses from its gaseous state in specialized vessels, showing chemical stability that makes it resistant in many environments, but vulnerable to certain oxidizing agents.

Mercury is stable in dry and humid air, forming a minimal surface layer of mercuric oxide (HgO) that does not compromise its integrity. It is insoluble in fresh and salt water, resisting corrosion in these media, which historically made it ideal for instruments like thermometers and barometers. In reducing acids, such as hydrochloric acid (HCl), mercury shows high resistance, reacting minimally. However, oxidizing acids, such as nitric acid (HNO₃), attack it rapidly, forming mercury nitrate (Hg(NO₃)₂) or other soluble compounds. Bases, such as sodium hydroxide (NaOH), do not significantly affect mercury, even at elevated temperatures, reinforcing its chemical nobility. Halogens, such as chlorine (Cl₂), react with mercury to form halides (like HgCl₂), although these reactions are controllable.

A unique aspect of mercury is its ability to act as a corrosive agent due to its liquid state. Unlike solid metals, mercury atoms in the liquid state are in constant motion, which increases their chemical reactivity by facilitating bond formation. This phenomenon allows mercury to form amalgams, solid or semi-solid alloys with metals such as aluminum (Al), copper (Cu), silver (Ag), gold (Au), and zinc (Zn), which dissolve in mercury upon contact, as if they were "absorbed". For example, in the production of dental amalgams (typically ~50% Hg with Ag and Sn), solid metals are mixed with liquid mercury, which acts as a natural "solvent" due to its molten state, analogous to molten copper incorporating tin in bronze production. These amalgams have low melting points, depending on the composition, which makes them useful in specific applications.

However, not all metals are compatible with mercury. Iron (Fe) is a notable exception, as it does not form amalgams, even with prolonged contact, due to its low chemical affinity with mercury. This property made iron a common material for storing mercury in antiquity. Other metals, such as lead (Pb), also show limited compatibility. The reactivity of mercury as a liquid does not imply an intrinsic ability to dissolve metals, but rather depends on its molten state and chemical affinity with each metal. Its corrosion resistance, combined with its ability to corrode other metals, makes it unique, but its toxicity (classified as a heavy metal with neurological and renal risks) and volatility require careful handling, especially in applications where spills can contaminate the environment.

Mercury (Hg), a chemical element with atomic number 80, is unique among metals for being liquid at ambient temperature and pressure (0–25 °C, 1 atm), with a melting point of -38.83 °C and a density of 13.53 g/cm³. This property distinguishes it from most metals, which are solid under standard conditions due to strong metallic bonds in their crystal lattices. The reason for its liquid state lies in the weakness of the Hg–Hg bonds, influenced by relativistic effects in its electronic structure ([Xe] 4f¹⁴ 5d¹⁰ 6s²), which contrast with metals like tungsten (W), whose high melting point (3,422 °C) reflects extremely strong bonds. This phenomenon, though complex, explains why mercury and, to a lesser extent, gallium (Ga, melting point 29.76 °C) are liquid under near-ambient conditions.

The key to mercury's liquid state resides in the weakness of its metallic bonds. In metals, atoms form a crystal lattice where delocalized electrons create strong bonds, responsible for high melting points in refractory metals like tungsten, whose W–W bond is robust due to high electron density and atomic cohesion. In mercury, the 6s electrons are stabilized by relativistic effects, which make the outer electron shell less available for forming strong metallic bonds. This results in a weak Hg–Hg interaction, with larger interatomic distances than in solid metals, producing a viscous and dense liquid state that does not exhibit the typical metallic luster in motion, appearing almost like an exotic substance. However, the bonds are strong enough to prevent mercury from being a gas under normal conditions, unlike elements with even weaker bonds, which would require extreme cooling to condense.

Gallium, also from group 13, shows similar behavior, but its Ga–Ga bonds are stronger, resulting in a slightly higher melting point (29.76 °C), which makes it liquid in warm environments. In both cases, alloys tend to have lower melting points than pure metals, following the rule that the melting point decreases with a higher percentage of the lower melting point component. For example, Galinstan (an alloy of gallium, indium (In), and tin (Sn)) is liquid at room temperature, while mercury amalgams with metals like silver (Ag) or gold (Au) have lower melting points than the pure alloying metals. In contrast, alloys like tungsten steels have higher melting points than iron (Fe, ~1,538 °C) but lower than pure tungsten, illustrating how mixing affects thermal properties.

The complete explanation of mercury's liquid state involves advanced concepts of quantum physics, such as the relativistic contraction of the 6s orbitals, but in essence, its low atomic cohesion, compared to more rigid metals, allows it to remain liquid over a range of temperatures where other metals are solid. This property, along with its high density and corrosion resistance in non-oxidizing environments, has made it historically valuable in applications such as thermometers, although its toxicity (~60 days biological half-life) limits its modern use. Mercury, with its unique behavior, stands out as a fascinating example of how electronic structure determines the physical properties of an element.

Mercury (Hg), a chemical element with atomic number 80, is a liquid metal at room temperature (0–25 °C, 1 atm) with a density of 13.53 g/cm³ and an abundance of 0.08 ppm in the Earth's crust. Its liquid state, toxicity, and unique chemical properties have limited its applications, especially in recent decades due to regulations such as the Minamata Convention (2013), which restricts its use due to environmental and health risks. Although historically valuable for its fluidity and ability to form amalgams, mercury has been replaced in many applications by safer alternatives, such as eutectic alloys like Galinstan (gallium, indium, tin). Its current use (3,000 tons annually in 2025) is concentrated in specialized sectors and, to a lesser extent, in countries with less strict regulations.

Historically, mercury was crucial in the extraction and treatment of gold (Au). In mining, it was used to dissolve gold dispersed in rocks, forming an amalgam that was then heated (~600 °C) to evaporate the mercury and precipitate pure gold. This practice, still employed in artisanal mining in developing countries, is highly polluting due to the release of mercury vapors. In the past, the French technique of ormolu (gilded bronze) used mercury to apply gold coatings to luxury furniture and clocks. Pulverized gold was mixed with liquid mercury, which acted as a vehicle to "paint" the surface, but the process generated toxic vapors, causing numerous casualties among artisans. This technique is obsolete in Europe due to health and safety concerns.

In medicine, mercury was used in dental amalgams, solid alloys (~50% Hg with silver, Ag; copper, Cu; and tin, Sn) that filled tooth cavities after caries removal. These amalgams, resistant to corrosion and the mechanical wear of chewing, were durable and adhered well to the tooth, often lasting decades. However, their mercury content has led to a decline in their use, especially in developed countries, where non-toxic composite resins are preferred. Silver, a common component, increased the cost of amalgams. Mercury was also part of merbromin (C₂₀H₈Br₂HgNa₂O₆, known as Mercurochrome), a topical antiseptic for small to medium wounds. Although effective, its use has been restricted in many countries due to its toxicity, but it persists in less regulated regions, such as some developing countries.

In instrumentation, mercury's inability to "wet" glass (it does not react with SiO₂) and its high density made it ideal for thermometers and barometers, used in medicine and laboratories to measure temperature and pressure. Its fluidity and precise thermal response were advantages, but the risks of spills and vapor exposure have led to its replacement by alcohol or digital thermometers and alloys like Galinstan, which solidifies at ~-19 °C and is less toxic. In electronics, mercury is used in cold cathode lamps (fluorescent and mercury vapor lamps), where it acts as a catalyst to generate ultraviolet light, which excites a phosphorescent coating. However, these lamps are being replaced by safer LED technologies.

Although mercury remains relevant in applications such as electrolytic cells and some industrial processes, its use is in decline due to its toxicity (biological half-life of ~60 days) and the development of alternatives like Galinstan, whose exact composition, patented by Geratherm Medical AG, remains a standard in low-temperature applications. The combination of its liquid state, chemical nobility, and ability to form amalgams has made mercury a historically fascinating material, but its environmental and health impact has restricted its role in modern technology.

Mercury (Hg), a chemical element with atomic number 80, is a liquid metal at room temperature (0–25 °C, 1 atm) with a density of 13.53 g/cm³ and an abundance of ~0.08 ppm in the Earth's crust. Classified as a heavy metal, mercury is highly toxic, with harmful effects on human health and the environment that have led to strict restrictions on its use, such as the Minamata Convention (2013). Its toxicity, combined with its volatility and ability to accumulate in living organisms, makes it a dangerous material, especially in its elemental form and in compounds like methylmercury. Although its silvery sheen and liquid state make it fascinating, its handling requires extreme caution, which explains the difficulty in acquiring it, even for collectors, and its progressive withdrawal from the public market.

Mercury is dangerous due to its ability to affect the nervous system, kidneys, and liver. Its toxicity depends on the chemical form: elemental mercury (Hg⁰) is less toxic by skin contact, but its vapors, generated by its high volatility (vapor pressure ~0.0018 mmHg at 20 °C), are extremely dangerous when inhaled, causing tremors, neurological damage, and cognitive problems. Methylmercury, formed by microbial processes in aquatic environments, is even more toxic, accumulating in the food chain, especially in fish and shellfish, leading to poisoning from consumption (such as the case of Minamata Bay, Japan, in the 1950s). With a biological half-life of ~60 days, mercury accumulates in the body, exacerbating its effects. Chronic exposure can cause mercurialism, with symptoms such as memory loss, tremors, and renal failure, while acute exposure, although rare, can be fatal, especially in children who ingest or manipulate the metal.

The manipulation of elemental mercury, such as children playing with its shiny drops or spilling it, poses significant risks. Spills in aquatic environments are particularly dangerous, as mercury disperses, converts into methylmercury, and contaminates drinking water or food, affecting both humans and ecosystems. For example, in rivers and oceans, mercury can bioaccumulate in fish, reaching concentrations thousands of times higher than in the surrounding water. This environmental danger, along with the possibility of accidental exposure in uncontrolled environments, has led to its exclusion from products such as thermometers and dental amalgams in many countries, replaced by alternatives like Galinstan (an alloy of gallium, indium, and tin) or composite resins.

The perception that mercury could be used to manufacture explosives or "bombs" is unfounded, as it has no inherent properties for such a purpose. However, its toxicity and potential for misuse have contributed to its strict regulation, making it more difficult to acquire than materials like depleted uranium, which, although expensive, is more controlled but less restricted in certain industrial contexts. The idea of a "conspiracy" to transmute the Hg-196 isotope into gold (Au) using cyclotrons is scientifically possible but impractical: nuclear transmutation produces insignificant amounts of gold (on the order of millions of atoms, compared to ~10²³ atoms in a grain of sand), ruling out any economic or conspiratorial motivation. Instead, restrictions respond to legitimate concerns about health and the environment, with regulations like RoHS limiting its use in electronics to less than 0.1% by weight.

In summary, mercury is extremely dangerous due to its toxicity, volatility, and bioaccumulation, especially in aquatic environments. Its handling requires specialized facilities, protective equipment (such as respirators), and containment systems to prevent spills. Although its visual appeal and unique properties make it coveted by collectors, its restricted access reflects the need to protect public health and ecosystems, relegating its use to controlled industrial applications, such as electrolytic cells and certain lamps, where alternatives are not yet viable.

Mercury (Hg), a chemical element with atomic number 80, is a liquid metal at room temperature (0–25 °C, 1 atm) with a density of 13.53 g/cm³ and an abundance of ~0.08 ppm in the Earth's crust. Classified as a heavy metal, mercury is highly toxic, with severe effects on human health and the environment due to its ability to infiltrate the body through inhalation of vapors, ingestion, or dermal contact. Its volatility (vapor pressure ~0.0018 mmHg at 20 °C) and bioaccumulation, especially in the form of methylmercury, make it a significant danger, which has led to strict regulations, such as the Minamata Convention (2013), to limit its use in applications like thermometers, dental amalgams, and lamps.

The adverse effects of mercury are severe due to its ability to accumulate in the body, with a biological half-life of ~60 days. Vapors of elemental mercury (Hg⁰), which begin to be released significantly from ~40 °C, are particularly dangerous when inhaled, as they easily cross lung membranes and distribute to the brain and spinal cord. Chronic exposure causes mercurialism, with symptoms including tremors, memory loss, irritability, and severe mental disorders, often irreversible, such as dementia or psychosis. Methylmercury, formed in aquatic environments by microbial action, accumulates in the food chain (especially in fish), affecting the nervous, renal, and hepatic systems, and is especially harmful to fetuses and children, causing developmental neurological delays. Acute exposure, although less common, can be fatal, and the elimination of mercury from the body is difficult, as there are no efficient methods to extract it after poisoning, leading to permanent damage.

Precautions for handling mercury are critical to minimize risks. It is essential to educate children and adults about the dangers of manipulating this metal, avoiding direct contact, such as playing with its shiny drops, due to its visual appeal but high toxicity. Mercury is not an "enemy" with intentions, but an inert chemical element whose danger lies in its physical and chemical properties. In industrial settings, such as mining or lamp manufacturing, the use of personal protective equipment, including respirators and gloves, is required to prevent inhalation of vapors or skin contact. Ventilation and containment systems are necessary to capture vapors and prevent spills, which are especially dangerous in aquatic environments, where mercury can transform into methylmercury and contaminate drinking water or food. Waste management, such as mercury batteries or lamps, must be carried out in specialized facilities to prevent infiltration into the soil or water. Regulations like the RoHS directive limit its use in electronics to less than 0.1% by weight, promoting alternatives like Galinstan (an alloy of gallium, indium, and tin) for thermometers.

The handling of mercury must be strictly controlled, and public education is key to preventing accidental exposures. Its toxicity, especially its impact on the nervous system and its environmental persistence, makes it a high-risk material that requires extreme caution, relegating its use to essential industrial applications where alternatives are not yet viable.

Mercury (Hg), a chemical element with atomic number 80, is a liquid metal at room temperature (0–25 °C, 1 atm) with a density of 13.53 g/cm³ and an abundance of ~0.08 ppm in the Earth's crust. Beyond its physical properties and toxicity, mercury has played a significant role in culture, mythology, and historical science, from alchemy to astrology, and has left its mark on modern popular culture. Its liquid state, silvery sheen, and rarity made it a symbol of transformation and mystery, reflected in ancient traditions and contemporary representations, though often distorted.

In alchemy, mercury held a central place as one of the fundamental pillars of matter, along with sulfur (S) and, to a lesser extent, salt. Alchemists believed that all metals were composed of these substances in different proportions, transformed by natural processes. Mercury, considered the "primordial form" of matter, was contrasted with lead (Pb), seen as the "oldest" or least pure metal. This theory, though erroneous, postulated that metals like copper (Cu), iron (Fe), or tin (Sn) arose from variations in the mixture of mercury and sulfur. Although alchemists were unaware of atomic structure (defined by the number of protons), their idea of a common underlying matter was not entirely misguided, as all elements share protons, neutrons, and electrons. In this sense, their vision, though vague, poetically anticipated the fundamental unity of matter, discovered centuries later with the modern atomic model.

In astrology, mercury is associated with the zodiac signs Gemini and Virgo, as well as the planet Mercury, which bears the name of the Roman god of the same name (equivalent to the Greek Hermes). This link reflects qualities of communication, mental agility, and adaptability, attributed both to the god and to the metal for its fluidity and versatility. Although in Greek mythology there are no direct references to mercury as a metal, in late alchemy (15th–17th centuries) these associations merged, connecting the metal with Hermes as a symbol of transformation and transmutation, a central concept in the search for the philosopher's stone.

In popular culture, mercury appears in role-playing and fantasy video games under names like "quicksilver" or "azogue" (from Arabic az-za'ūq, mercury). In these contexts, it is represented as an exotic and powerful material, often superior to steel, which in games is usually the most common and weakest metal. However, these representations are purely fictional, as real mercury, liquid and fragile in its solid state, has no structural applications or resistance properties comparable to steel (Fe-C). Its inclusion as "quicksilver" reflects its historical fascination, but not its chemical reality. Currently, the use of mercury (~3,000 tons annually in 2025) is restricted due to its toxicity, limiting it to industrial applications such as electrolytic cells and catalysts, while its cultural legacy endures in alchemy, astrology, and popular imagination.