Kamerlingh Onnes Award
The Kamerlingh Onnes Award is in recognition of special merits of scientists active in the field of refrigeration technology and more low-temperature science and technology. It was founded in 1948 by the Royal Dutch Association of Refrigeration The name of the award is intended to keep the memory of Heike Kamerlingh Onnes alive; the award is assigned every four years and the winners get a golden medal and a certificate. 1950 Prof. F. Simon, England, Very low temperatures, liquid hydrogen and helium 1955 Prof. R. Plank, Germany, Refrigeration technology in a broad sense 1958 Prof. S. C. Collins, M. I. T. USA, Low temperatures with regard to equipment for the production of liquid helium 1958 Philips Natuurkundig Laboratorium, Netherlands, Development of cryogenerator 1963 Dr. F. Kidd and Dr. C. West, England, Research storage conditions of fruit 1968 Prof. P. L. Kapitza, Russia, Low temperatures. F. Kunzler, Bell Labs. USA, Superconductivity 1983 Prof. L. Váhl, The Netherlands, Refigeration technology in the broad sense 1988 Ir.
T. A. van Hiele, Netherlands, Application of refrigeration technology on agricultural and horticultural products 1989 Dr. T. Meryman, American Red Cross, USA, Preservation of blood and organs 1995 Prof. R. Cohen, Purdue University, USA, Compressor technology and international knowledge transfer 1995 Refrigerator Research group at the Massey University, New Zealand, under Prof. A. C. Cleland, Food refrigeration processes and knowledge transfer 2000 Prof. G. Frossati, Kamerlingh Onnes Lab. Netherlands, Development of cryogenic equipment, in particular as regards dilution refrigerators 2008 Prof. H. C. Kruse, Germany, Contributed to technological progress and knowledge transfer and did meritorious work for cold and heat pump associations 2008 Prof. A. T. A. M. de Waele, Netherlands, Optimization of pulse tube refrigerators for temperatures below 4 K 2012 Dr. P. Lebrun, CERN, For his groundbreaking contributions to the field of cryogenic science and technology making the Large Hadron Collider possible
Arnhem is a city and municipality situated in the eastern part of the Netherlands. It is the capital of the province of Gelderland and located on both banks of the rivers Nederrijn and Sint-Jansbeek, the source of the city's development. Arnhem is one of the larger cities of the Netherlands; the municipality is part of the Arnhem-Nijmegen Metropolitan Area which has a combined 736,500 inhabitants. Arnhem is home to the Hogeschool van Arnhem en Nijmegen, ArtEZ Institute of the Arts, Netherlands Open Air Museum, Airborne Museum'Hartenstein', Royal Burgers' Zoo, NOC*NSF and National Sports Centre Papendal; the north corner of the municipality is part of the Hoge Veluwe National Park. It is 55 square kilometers in area, consisting of heathlands, sand dunes, woodlands; the oldest archeological findings of human activity around Arnhem are two firestones of about 70,000 years ago. These come from the stone age. In Schuytgraaf, remnants of a hunters camp from around 5000 BC have been discovered. In Schaarsbergen, twelve grave mounds were found from 2400 BC, which brought the so-called Neolithic Revolution to the area of Arnhem, which meant the rise of the farmers.
The earliest settlement in Arnhem dates from 1500 BC, of which traces have been found on the Hoogkamp, where the Van Goyenstraat is located. In the inner city, around the Sint-Jansbeek, traces of settlement have been found from around 700 BC, while the first traces south of the Rhine have been found dating to around 500 BC, in the Schuytgraaf. Though the early tracks of settlements did show that the early residents of Arnhem descended from the forests on the hills, Arnhem was not built on the banks of the river Rhine, but a little higher along the Sint-Jansbeek. Arnhem arose on the location where the road between Utrecht and Zutphen split. Seven streams provided the city with water, only when the flow of the Rhine was changed in 1530, was the city located on the river. Arnhem was first mentioned as such in 893 as Arentheym. In 1233, Count Otto II of Guelders from Zutphen, conferred city rights on the town, which had belonged to the abbey of Prüm, settled in, fortified it. Arnhem entered the Hanseatic League in 1443.
In 1473, it was captured by Charles the Bold of Burgundy. In 1514, Charles of Egmond, duke of Guelders, took it from the dukes of Burgundy; as capital of the so-called "Kwartier van Veluwe" it joined the Union of Utrecht during the Eighty Years' War in 1579. After its capture from the Spanish forces by Dutch and English troops in 1585 the city became part of the Republic of the Seven United Provinces of the Netherlands; the French occupied the town from 1672 to 1674. From 1795 to 1813, it was reoccupied by both revolutionary and imperial forces. In the early 19th century, the former fortifications were completely dismantled, to give space for town expansion; the Sabelspoort is the only remaining part of the medieval walls. In the 19th century, Arnhem was a genteel resort town famous for its picturesque beauty, it was known as "het Haagje van het oosten" because a number of rich former sugar barons or planters from the Indies settled there, as they did in The Hague. Now the city is famous for its parks and greenery.
The urbanization in the north on hilly terrain is quite unusual for the Netherlands. In the Second World War, during Operation Market Garden, the British 1st Airborne Division, under the command of Major-General Roy Urquhart, the Polish 1st Independent Parachute Brigade were given the task of securing the bridge at Arnhem. Glider infantry and paratrooper units were landed into the area on 17 September and later; the bulk of the force never met their objective. A small element of the British 1st Airborne, the 2nd Parachute Battalion under Lieutenant Colonel John D. Frost, managed to make its way as far as the bridge but was unable to secure both sides; the British troops encountered stiff resistance from the German 9th and 10th SS Panzer Divisions, stationed in and around the city. The British force at the bridge ran out of ammunition and was captured on 21 September, a full withdrawal of the remaining forces was made on 26 September; these events were dramatized in the 1977 movie A Bridge Too Far..
As a tribute, the rebuilt bridge was renamed'John Frost Bridge' after the commander of the paratroopers. The official commemoration is 17 September; the current bridge is the third almost-identical bridge built at the same spot. The Dutch Army destroyed the first bridge when the German Army invaded the Netherlands in 1940; the second bridge was destroyed by the United States Army Air Forces shortly after the 1944 battle. A second battle of Arnhem took place in April 1945 when the city was liberated by the British 49th Infantry Division fighting as part of the First Canadian Army. Just outside Arnhem, in the town of Oosterbeek the Commonwealth War Graves Commission built the Arnhem Oosterbeek War Cemetery which contains the graves of most of those killed during the September landings, many of those killed in fighting in the area; the municipality of Arnhem consists of the city of Arnhem and the following surrounding suburbs and former villages: Elden, Netherlands (former village, now surro
Enthalpy, a property of a thermodynamic system, is equal to the system's internal energy plus the product of its pressure and volume. In a system enclosed so as to prevent matter transfer, for processes at constant pressure, the heat absorbed or released equals the change in enthalpy; the unit of measurement for enthalpy in the International System of Units is the joule. Other historical conventional units still in use include the calorie. Enthalpy comprises a system's internal energy, the energy required to create the system, plus the amount of work required to make room for it by displacing its environment and establishing its volume and pressure. Enthalpy is defined as a state function that depends only on the prevailing equilibrium state identified by the system's internal energy and volume, it is an extensive quantity. Enthalpy is the preferred expression of system energy changes in many chemical and physical measurements at constant pressure, because it simplifies the description of energy transfer.
In a system enclosed so as to prevent matter transfer, at constant pressure, the enthalpy change equals the energy transferred from the environment through heat transfer or work other than expansion work. The total enthalpy, H, of a system cannot be measured directly; the same situation exists in classical mechanics: only a change or difference in energy carries physical meaning. Enthalpy itself is a thermodynamic potential, so in order to measure the enthalpy of a system, we must refer to a defined reference point; the ΔH is a positive change in endothermic reactions, negative in heat-releasing exothermic processes. For processes under constant pressure, ΔH is equal to the change in the internal energy of the system, plus the pressure-volume work p ΔV done by the system on its surroundings; this means that the change in enthalpy under such conditions is the heat absorbed or released by the system through a chemical reaction or by external heat transfer. Enthalpies for chemical substances at constant pressure refer to standard state: most 1 bar pressure.
Standard state does not speaking, specify a temperature, but expressions for enthalpy reference the standard heat of formation at 25 °C. Enthalpy of ideal gases and incompressible solids and liquids does not depend on pressure, unlike entropy and Gibbs energy. Real materials at common temperatures and pressures closely approximate this behavior, which simplifies enthalpy calculation and use in practical designs and analyses; the word enthalpy was coined late, in the early 20th century, in analogy with the 19th-century terms energy and entropy. Where energy uses the root of the Greek word ἔργον "work" to express the idea of "work-content" and where entropy uses the Greek word τροπή "transformation" to express the idea of "transformation-content", so by analogy, enthalpy uses the root of the Greek word θάλπος "warmth, heat" to express the idea of "heat-content"; the term does in fact stand in for the older term "heat content", a term, now deprecated as misleading, as dH refers to the amount of heat absorbed in a process at constant pressure only, but not in the general case.
Josiah Willard Gibbs used the term "a heat function for constant pressure" for clarity. Introduction of the concept of "heat content" H is associated with Benoît Paul Émile Clapeyron and Rudolf Clausius; the term enthalpy first appeared in print in 1909. It is attributed to Heike Kamerlingh Onnes, who most introduced it orally the year before, at the first meeting of the Institute of Refrigeration in Paris, it gained currency only in the 1920s, notably with the Mollier Steam Tables and Diagrams, published in 1927. Until the 1920s, the symbol H was used, somewhat inconsistently, for "heat" in general; the definition of H as limited to enthalpy or "heat content at constant pressure" was formally proposed by Alfred W. Porter in 1922; the enthalpy of a thermodynamic system is defined as H = U + p V, where H is enthalpy U is the internal energy of the system p is pressure V is the volume of the systemEnthalpy is an extensive property. This means, it is convenient to introduce the specific enthalpy h = H m, where m is the mass of the system, or the molar enthalpy H m = H n, where n is the number of moles.
For inhomogeneous systems the enthalpy is the sum of the enthalpies of the composing subsystems: H = ∑ k H k, where H is the total enthalpy of all the subsystems k refers to the various subsystems H k refers to the enthalpy of each subsystem ∑ k
Leiden is a city and municipality in the province of South Holland, Netherlands. The municipality of Leiden had a population of 123,856 in August 2017, but the city forms one densely connected agglomeration with its suburbs Oegstgeest, Leiderdorp and Zoeterwoude with 206,647 inhabitants; the Netherlands Central Bureau of Statistics further includes Katwijk in the agglomeration which makes the total population of the Leiden urban agglomeration 270,879, in the larger Leiden urban area Teylingen and Noordwijkerhout are included with in total 348,868 inhabitants. Leiden is located on the Oude Rijn, at a distance of some 20 kilometres from The Hague to its south and some 40 km from Amsterdam to its north; the recreational area of the Kaag Lakes lies just to the northeast of Leiden. A university city since 1575, Leiden has been one of Europe's most prominent scientific centres for more than four centuries. Leiden is a typical university city, university buildings are scattered throughout the city and the many students from all over the world give the city a bustling and international atmosphere.
Many important scientific discoveries have been made here, giving rise to Leiden's motto: ‘City of Discoveries’. The city houses Leiden University, the oldest university of the Netherlands, Leiden University Medical Center. Leiden University is one of Europe's top universities, with thirteen Nobel Prize winners, it is a member of the League of European Research Universities and positioned in all international academic rankings. It is twinned with the location of the United Kingdom's oldest university. Leiden University and Leiden University of Applied Sciences together have around 35,000 students. Modern scientific medical research and teaching started in the early 18th century in Leiden with Boerhaave. Leiden is a city with a rich cultural heritage, not only in science, but in the arts. One of the world's most famous painters, was born and educated in Leiden. Other famous Leiden painters include Jan van Goyen and Jan Steen. Leiden was formed on an artificial hill at the confluence of the rivers Nieuwe Rijn.
In the oldest reference to this, from circa 860, the settlement was called Leithon. The name is said to be from Germanic *leitha- "canal" in dative pluralis, thus meaning "at the canals". "Canal" is not the proper word. A leitha was a human-modified natural river natural artificial. Leiden has in the past erroneously been associated with the Roman outpost Lugdunum Batavorum; this particular castellum was thought to be located at the Burcht of Leiden, the city's name was thought to be derived from the Latin name Lugdunum. However the castellum was in fact closer to the town of Katwijk, whereas the Roman settlement near modern-day Leiden was called Matilo; the landlord of Leiden, situated in a stronghold on the hill, was subject to the Bishop of Utrecht but around 1100 the burgraves became subject to the county of Holland. This county got its name in 1101 from a domain near the stronghold: Holland. Leiden was sacked in 1047 by Emperor Henry III. Early 13th century, Countess of Holland took refuge here when she was fighting in a civil war against her uncle, William I, Count of Holland.
He captured Ada. Leiden received city rights in 1266. In 1389, its population had grown to about 4,000 persons. In 1420, during the Hook and Cod wars, Duke John III of Bavaria along with his army marched from Gouda in the direction of Leiden in order to conquer the city since Leiden did not pay the new Count of Holland Jacqueline, Countess of Hainaut, his niece and only daughter of Count William VI of Holland. Burgrave Filips of Wassenaar and the other local noblemen of the Hook faction assumed that the duke would besiege Leiden first and send small units out to conquer the surrounding citadels, but John of Bavaria chose to attack the citadels first. He rolled the cannons along with his army but one, too heavy went by ship. By firing at the walls and gates with iron balls the citadels fell one by one. Within a week John of Bavaria conquered the castles of Poelgeest, Ter Does, Hoichmade, de Zijl, ter Waerd, Warmond and de Paddenpoel. On 24 June the army appeared before the walls of Leiden. On 17 August 1420, after a two-month siege the city surrendered to John of Bavaria.
The burgrave Filips of Wassenaar was stripped of his offices and rights and lived out his last years in captivity. Leiden flourished in the 17th century. At the close of the 15th century the weaving establishments of Leiden were important, after the expulsion of the Spaniards Leiden cloth, Leiden baize and Leiden camlet were familiar terms. In the same period, Leiden developed an important publishing industry; the influential printer Christoffel Plantijn lived there at one time. One of his pupils was Lodewijk Elzevir, who established the largest bookshop and printing works in Leiden, a business continued by his descendants through 1712 and the name subsequently adopted by contemporary publisher Elsevier. In 1572, the city sided with the Dutch revolt against Spanish rule and played an important role in the Eighty Years' War. Besieged from May until October 1574 by the Spanish, Leiden was relieved by the cutting of the dikes, thus enabling ships to carry provisions to the inhabitants of the flooded town.
As a reward for the heroic defence of the previous year, the University of Leiden was founded by William I of Orange in 1575. Yearly on 3 Oc
Groningen is the main municipality as well as the capital city of the eponymous province in the Netherlands. It is the largest city in the north of the Netherlands and has 230,000 inhabitants; the Groningen-Assen metropolitan area has about half a milion inhabitants. Groningen is an old city and was the regional power of the north of the Netherlands, a semi-independent city-state and member of the German Hanseatic League. Groningen is a university city, with an estimated 31,000 students at the University of Groningen, an estimated 29,000 at the Hanze University of Applied Sciences; the city was founded at the northernmost point of the Hondsrug area. The oldest document referring to Groningen's existence dates from 1040. However, the city existed long before then: the oldest archaeological traces found are believed to stem from the years 3950–3720 BC, although the first major settlement in Groningen has been traced back to the 3rd century AD. In the 13th century, when Groningen was an important trade centre, its inhabitants built a city wall to underline its authority.
The city made its dialect a common tongue. The most influential period of the city was the end of the 15th century, when the nearby province of Friesland was administered from Groningen. During these years, the Martinitoren 127 metres tall, was built; the city's independence ended in 1536, when it chose to accept Emperor Charles V, the Habsburg ruler of the other Netherlands, as its overlord. In 1594, until held by Spain, was captured by a Dutch and English force led by Maurice of Nassau. Soon afterwards the city and the province joined the Republic of the Seven United Provinces. In 1614, the University of Groningen was founded only for religious education. In the same period the city expanded and a new city wall was built; that same city wall was tested during the Third Anglo-Dutch War in 1672, when the city was attacked fiercely by the bishop of Münster, Bernhard von Galen. The city walls resisted, an event, still celebrated with music and fireworks on August 28; the city did not escape the devastation of World War II.
In particular, the main square, the Grote Markt, was destroyed in April 1945 in the Battle of Groningen. However, the Martinitoren, its church, the Goudkantoor, the city hall were not damaged; the battle lasted several days. Groningen has an oceanic temperate climate, like all of the Netherlands, although colder in winter than other major cities in the Netherlands due to its northeasterly position. Weather is influenced by the North Sea to the north-west and its prevailing north-western winds and gales. Summers are somewhat humid. Temperatures of 30 °C or higher occur sporadically. Rainy periods are common in spring and summer. Average annual precipitation is about 800 mm. Annual sunshine hours vary, but are below 1600 hours, giving much cloud cover similar to most of the Netherlands. Climate in this area has mild differences between highs and lows, there is adequate rainfall year-round; the Köppen Climate Classification subtype for this climate is "Cfb".. Winters are cool: on average above freezing, although frosts are common during spells of easterly wind from Germany and Siberia.
Night-time temperatures of −10 °C or lower are not uncommon during cold winter periods. The lowest temperature recorded is −26.8 °C on February 16, 1956. Snow falls, but stays long due to warmer daytime temperatures, although white snowy days happen every winter; the municipality of Groningen has grown rapidly. In 1968 it expanded by mergers with Hoogkerk and Noorddijk, in 2019 it merged with Haren and Ten Boer. All historical data are for the original city limits, excluding Hoogkerk, Noorddijk and Ten Boer; until there were two large sugar refineries within the city boundaries. The Suiker Unie plant was outside Groningen, but it was swallowed by the expansion of the city. After a campaign to close the factory, it was shut down in 2008/2009. Before closing down, its sugar production amounted to 250,000 tonnes of beet sugar, with 250 employees; the only remaining sugar factory is CSM Vierverlaten in Hoogkerk, which produces 235,000 tonnes of beet sugar, with 283 employees. Well known companies from Groningen are publishing company Noordhoff Uitgevers, tobacco company Royal Theodorus Niemeyer, health insurance company Menzis, distillery Hooghoudt, natural gas companies GasUnie and GasTerra.
There is an increased focus on business services. In addition, the hotel and catering industry forms a significant part of the economy of Groningen; the city is nationally known as the "Metropolis of the North" and as "Martinistad" referring to the tower of the Martinitoren, named after its patron saint Martin of Tours. Although Groningen is not a large city, it does have an important role as the main urban centre of this part of the country in the fields of music and other arts and business; the large number of students living in Groningen contributes to a diverse cultural scene for a city of its size. Since 2016 Groningen is host of the International Cycling Film Festival, an annual film festival for bicycle related films, it takes place in the art house cinema of the old Roman Catholic Hospital. The most famous museum in Groningen is
Superconductivity is a phenomenon of zero electrical resistance and expulsion of magnetic flux fields occurring in certain materials, called superconductors, when cooled below a characteristic critical temperature. It was discovered by Dutch physicist Heike Kamerlingh Onnes on April 1911, in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon, it is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor during its transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood as the idealization of perfect conductivity in classical physics; the electrical resistance of a metallic conductor decreases as temperature is lowered. In ordinary conductors, such as copper or silver, this decrease is limited by impurities and other defects. Near absolute zero, a real sample of a normal conductor shows some resistance.
In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current through a loop of superconducting wire can persist indefinitely with no power source. In 1986, it was discovered that some cuprate-perovskite ceramic materials have a critical temperature above 90 K; such a high transition temperature is theoretically impossible for a conventional superconductor, leading the materials to be termed high-temperature superconductors. The cheaply-available coolant liquid nitrogen boils at 77 K, thus superconduction at higher temperatures than this facilitates many experiments and applications that are less practical at lower temperatures. There are many criteria; the most common are: A superconductor can be Type I, meaning it has a single critical field, above which all superconductivity is lost and below which the magnetic field is expelled from the superconductor. These points are called vortices. Furthermore, in multicomponent superconductors it is possible to have combination of the two behaviours.
In that case the superconductor is of Type-1.5. It is conventional if it can be explained by the BCS theory or its derivatives, or unconventional, otherwise. A superconductor is considered high-temperature if it reaches a superconducting state when cooled using liquid nitrogen – that is, at only Tc > 77 K) – or low-temperature if more aggressive cooling techniques are required to reach its critical temperature. Superconductor material classes include chemical elements, ceramics, superconducting pnictides or organic superconductors. Most of the physical properties of superconductors vary from material to material, such as the heat capacity and the critical temperature, critical field, critical current density at which superconductivity is destroyed. On the other hand, there is a class of properties. For instance, all superconductors have zero resistivity to low applied currents when there is no magnetic field present or if the applied field does not exceed a critical value; the existence of these "universal" properties implies that superconductivity is a thermodynamic phase, thus possesses certain distinguishing properties which are independent of microscopic details.
The simplest method to measure the electrical resistance of a sample of some material is to place it in an electrical circuit in series with a current source I and measure the resulting voltage V across the sample. The resistance of the sample is given by Ohm's law as R = V / I. If the voltage is zero, this means. Superconductors are able to maintain a current with no applied voltage whatsoever, a property exploited in superconducting electromagnets such as those found in MRI machines. Experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation. Experimental evidence points to a current lifetime of at least 100,000 years. Theoretical estimates for the lifetime of a persistent current can exceed the estimated lifetime of the universe, depending on the wire geometry and the temperature. In practice, currents injected in superconducting coils have persisted for more than 23 years in superconducting gravimeters. In such instruments, the measurement principle is based on the monitoring of the levitation of a superconducting niobium sphere with a mass of 4 grams.
In a normal conductor, an electric current may be visualized as a fluid of electrons moving across a heavy ionic lattice. The electrons are colliding with the ions in the lattice, during each collision some of the energy carried by the current is absorbed by the lattice and converted into heat, the vibrational kinetic energy of the lattice ions; as a result, the energy carried by the current is being dissipated. This is the phenomenon of electrical Joule heating; the situation is different in a superconductor. In a conventional superconductor, the electronic fluid cannot be resolved into individual electrons. Instead, it consists of bound pairs of electrons known as Cooper pairs; this pairing is caused by an attractive force between electrons from the exchange of phonons. Due to quantum mechanics, the energy spectr
Mercury is a chemical element with symbol Hg and atomic number 80. It is known as quicksilver and was named hydrargyrum. A heavy, silvery d-block element, mercury is the only metallic element, liquid at standard conditions for temperature and pressure. Mercury occurs in deposits throughout the world as cinnabar; the red pigment vermilion is obtained by synthetic mercuric sulfide. Mercury is used in thermometers, manometers, sphygmomanometers, float valves, mercury switches, mercury relays, fluorescent lamps and other devices, though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being phased out in clinical environments in favor of alternatives such as alcohol- or galinstan-filled glass thermometers and thermistor- or infrared-based electronic instruments. Mechanical pressure gauges and electronic strain gauge sensors have replaced mercury sphygmomanometers. Mercury remains in use in scientific research applications and in amalgam for dental restoration in some locales.
It is used in fluorescent lighting. Electricity passed through mercury vapor in a fluorescent lamp produces short-wave ultraviolet light, which causes the phosphor in the tube to fluoresce, making visible light. Mercury poisoning can result from exposure to water-soluble forms of mercury, by inhalation of mercury vapor, or by ingesting any form of mercury. Mercury is a silvery-white liquid metal. Compared to other metals, it is a fair conductor of electricity, it has a freezing point of −38.83 °C and a boiling point of 356.73 °C, both the lowest of any stable metal, although preliminary experiments on copernicium and flerovium have indicated that they have lower boiling points. Upon freezing, the volume of mercury decreases by 3.59% and its density changes from 13.69 g/cm3 when liquid to 14.184 g/cm3 when solid. The coefficient of volume expansion is 181.59 × 10−6 at 0 °C, 181.71 × 10−6 at 20 °C and 182.50 × 10−6 at 100 °C. Solid mercury can be cut with a knife. A complete explanation of mercury's extreme volatility delves deep into the realm of quantum physics, but it can be summarized as follows: mercury has a unique electron configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d, 6s subshells.
Because this configuration resists removal of an electron, mercury behaves to noble gases, which form weak bonds and hence melt at low temperatures. The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus; the absence of a filled inner f shell is the reason for the somewhat higher melting temperature of cadmium and zinc, although both these metals still melt and, in addition, have unusually low boiling points. Mercury does not react with most acids, such as dilute sulfuric acid, although oxidizing acids such as concentrated sulfuric acid and nitric acid or aqua regia dissolve it to give sulfate and chloride. Like silver, mercury reacts with atmospheric hydrogen sulfide. Mercury reacts with solid sulfur flakes. Mercury dissolves many metals such as silver to form amalgams. Iron is an exception, iron flasks have traditionally been used to trade mercury.
Several other first row transition metals with the exception of manganese and zinc are resistant in forming amalgams. Other elements that do not form amalgams with mercury include platinum. Sodium amalgam is a common reducing agent in organic synthesis, is used in high-pressure sodium lamps. Mercury combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact. Since the amalgam destroys the aluminium oxide layer which protects metallic aluminium from oxidizing in-depth small amounts of mercury can corrode aluminium. For this reason, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft. Mercury embrittlement is the most common type of liquid metal embrittlement. There are seven stable isotopes of mercury, with 202Hg being the most abundant; the longest-lived radioisotopes are 194Hg with a half-life of 444 years, 203Hg with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives.
199Hg and 201Hg are the most studied NMR-active nuclei, having spins of 1⁄2 and 3⁄2 respectively. Hg is the modern chemical symbol for mercury, it comes from hydrargyrum, a Latinized form of the Greek word ὑδράργυρος, a compound word meaning "water-silver" – since it is liquid like water and shiny like silver. The element was named after the Roman god Mercury, known for his mobility, it is associated with the planet Mercury. Mercury is the only metal for which the al