Discovery of Nitrogen
In 1674 the English physician John Mayow demonstrated that air is not a single element, it is made up of different substances. He did this by showing that only a part of air is combustible. Most of it is not.
Almost a century later, Scottish chemist Joseph Black carried out more detailed work on air. After removing oxygen and carbon dioxide, part of the air remained.
Black used burning phosphorus as the final step in oxygen removal. (Burning phosphorus has a very high affinity for oxygen and is efficient at removing it completely.) Black then assigned further study of the gases in air to his doctoral student, Daniel Rutherford.
Rutherford built on Black’s work and in a series of steps thoroughly removed oxygen and carbon dioxide from air. He showed that, like carbon dioxide, the residual gas could not support combustion or living organisms. Unlike carbon dioxide, however, nitrogen was insoluble in water and alkali solutions. Rutherford reported his discovery in 1772 of ‘noxious air,’ which we now call nitrogen.
Swedish pharmacist Carl Scheele discovered nitrogen independently, calling it spent air.
Scheele absorbed oxygen in a number of ways, including using a mixture of sulfur and iron filings and burning phosphorus. After removing the oxygen, he reported a residual gas which would not support combustion and had between two-thirds and three-quarters of the volume of the original air. Scheele published his results in 1777, although it is thought the work was carried out in 1772.
Although Rutherford and Scheele are now jointly credited with nitrogen’s discovery, it appears to have been discovered earlier by Henry Cavendish, but not published.
Prior to 1772 (the precise date is unknown – Priestley refers to it in his work “Experiments and Observations Made in and Before the Year 1772″) Cavendish wrote to Joseph Priestley describing ‘burnt air’.
The ‘burnt air’ had been prepared by passing air repeatedly over red hot charcoal (removing the oxygen) and then bubbling the remaining gas through a solution of caustic potash (potassium hydroxide) which would have removed the carbon dioxide.
Cavendish wrote: “The specific gravity of this air was found to differ very little from that of common air; of the two, it seemed rather lighter. It extinguished flame, and rendered common air unfit for making bodies burn in the same manner as fixed air, but in a less degree, as a candle which burnt about 80″ in pure common air, and which went out immediately in common air mixed with 6/55 of fixed air, burnt about 26″ in common air mixed with the same portion of this burnt air.”
In 1790 the French chemist Jean-Antoine-Claude Chaptal named the element ‘nitrogen’ after experiments showed it to be a constituent of nitre, as potassium nitrate was called then.
Discovery of Silicon
Quartz (crystalline silicon dioxide) has been known to people for many thousands of years. Flint is a form of quartz, and tools made from flint were in everyday use in the stone age.
In 1789, the French chemist Antoine Lavoisier proposed that a new chemical element could be found in quartz. This new element, he said, must be very abundant. He was right, of course. Silicon accounts for 28% of the weight of Earth’s crust.
It is possible that in England, in 1808, Humphry Davy isolated partly pure silicon for the first time, but he did not realize it.
In 1811, French chemists Joseph L. Gay-Lussac and Louis Jacques Thénard may also have made impure silicon by reacting potassium with silicon tetrafluoride to produce a reddish brown solid which was probably amorphous silicon. They did not, however, attempt to purify this new substance.
In 1824, Swedish chemist Jöns Jakob Berzelius produced a sample of amorphous silicon, a brown solid, by reacting potassium fluorosilicate with potassium and purifying the product with repeated washing. He named the new element silicium.
At that time the concept of semiconductors lay a century in the future. Unaware that such materials existed and that silicon was an excellent example of a semiconductor, scientists debated whether the new element should be classed as a metal or a nonmetal.
Berzelius believed it was a metal, while Humphry Davy thought it was a nonmetal. The problem was that the new element was a better conductor of electricity than nonmetals, but not as good a conductor as a metal.
Silicon was given its name in 1831 by Scottish chemist Thomas Thomson. He retained part of Berzelius’s name, from ‘silicis,’ meaning flint. He changed the element’s ending to on because the element was more similar to nonmetals boron and carbon than it was to metals such as calcium and magnesium. (Silicis, or flint, was probably our first use of silicon dioxide.)
In 1854, Henri Deville produced crystalline silicon for the first time. He did this by electrolyzing an impure melt of sodium aluminum chloride to produce aluminum silicide. The aluminum was removed with water, leaving silicon crystals.
Discovery of Boron
Boron compounds such as borax (sodium tetraborate, Na2B4O7·10H2O) have been known and used by ancient cultures for thousands of years. Borax’s name comes from the Arabic buraq, meaning “white.”
Boron was first partially isolated in 1808 by French chemists Joseph L. Gay-Lussac and L. J. Thénard and independently by Sir Humphry Davy in London. Gay-Lussac & Thénard reacted boric acid with magnesium or sodium to yield boron, a gray solid. They believed it shared characteristics with sulfur and phosphorus and named it bore.
Davy first tried to produce boron by electrolysis of boric acid, but was not satisfied with the results.
He enjoyed greater success reacting boric acid with potassium in a hydrogen atmosphere.
The result was a powdery substance.
Davy commented the substance was, “of the darkest shades of olive. It is opake, very friable, and its powder does not scratch glass.” After carrying out a number of chemical reactions to verify the uniqueness of the substance, Davy wrote, “there is strong reason to consider the boracic basis as metallic in nature, and I venture to propose for it the name of boracium.”
Neither party had, in fact, produced pure boron. Their samples were only about 60% pure.
In 1909, American chemist Ezekiel Weintraub was able to produce 99% pure boron, by reducing boron halides with hydrogen.
Almost a century later, in 2004, Jiuhua Chen and Vladimir L. Solozhenko produced a new form of boron, but were uncertain of its structure.
In 2009, a team led by Artem Oganov was able to demonstrate the new form of boron contains two structures, B12 icosohedra and B2 pairs. Gamma-boron, as it has been called, is almost as hard as diamond and more heat-resistant than diamond.
Talking about boron’s part metal, part non-metal properties, Oganov said, “Boron is a truly schizophrenic element. It’s an element of complete frustration. It doesn’t know what it wants to do. The outcome is something horribly complicated.”
Discovery of Aluminum
People have used alum since ancient times for dyeing, tanning and to stop bleeding. Alum is potassium aluminum sulfate.
In the 1750s German chemist Andreas Marggraf found he could use an alkali solution to precipitate a new substance from alum. Marggraf had previously been the first person to isolate zinc in 1746.
The substance Marggraf obtained from alum was named alumina by French chemist Louis de Morveau in 1760. We now know that alumina is aluminum oxide – chemical formula Al2O3.
De Morveau believed alumina contained a new metallic element, but, like Marggraf, he was unable to extract this metal from its oxide.
In 1807 or 1808, English chemist Humphry Davy decomposed alumina in an electric arc to obtain a metal. The metal was not pure aluminum, but an alloy of aluminum and iron.
Davy called the new metal alumium, then renamed it aluminum.
Aluminum was first isolated in 1825 by Hans Christian Ørsted (Oersted) in Copenhagen, Denmark who reported, “a lump of metal which in color and luster somewhat resembles tin.”
Ørsted produced aluminum by reducing aluminum chloride using a potassium-mercury amalgam. The mercury was removed by heating to leave aluminum.
German chemist Friedrich Wöhler (Woehler) repeated Ørsted’s experiment but found it yielded only potassium metal. Wöhler developed the method further two years later, reacting volatalized aluminum trichloride with potassium to produce small amounts of aluminum. In 1856 Berzelius stated that it was Wöhler who had succeeded in 1827. Wöhler is therefore usually given credit for the discovery.
More recently, Fogh repeated the original experiments and has shown that Ørsted’s method can give satisfactory results.
This has strengthened the priority of Ørsted’s original work and his position as discoverer of aluminum.
For almost three decades, aluminum remained a novelty, expensive to produce and more valuable than gold, until in 1854 Henri Saint-Claire Deville in Paris, France found a way of replacing potassium with much cheaper sodium in the reaction to isolate aluminum. Aluminum then became more popular but, because it was still quite expensive, was used in ornamental rather than practical situations.
Finally, in 1886 American chemist Charles Martin Hall and French chemist Paul Héroult independently invented the Hall-Héroult process, which inexpensively isolates aluminum metal from its oxide electrolytically.
Aluminum is still manufactured using the Hall-Héroult process today.
Discovery of Silver
Silver has been in use since prehistoric times. We do not know who its discoverer was, although the discovery would almost certainly have been of native silver.
Nuggets of native silver metal can be found in minerals and sometimes in rivers; but they are rare. Despite native silver’s rarity, very large pieces of it have been found, such as “pieces of native silver as big as stove lids and cannon balls” found in the early 1900s in Northern Ontario, Canada.
Silver has a special place in the history of the elements because it is one of the first five metals discovered and used by humans. The others were gold, copper, lead and iron.
Silver objects dating from before 4000 BC have been found in Greece and from slightly later in Anatolia (in modern Turkey). Silver artifacts have been found in the Sumerian city of Kish dating from about 3000 BC.
Silver and lead often appear together in nature, for example in the mineral galena which is mainly lead sulfide. Galena actually looks metallic (see image) and would have caught the eyes of people looking for metals.
The silver objects found in Greece, Turkey and Kish were made of silver that was refined from lead-containing ores such as galena. (Humans have been successful chemists for a surprisingly long time.)
First the ore was smelted under reducing conditions to obtain a mixture of silver and lead. The metals then went through cupellation: the metals were heated to about 1000 oC in a strong stream of air. Under these conditions lead reacts with oxygen forming lead oxide, leaving liquid silver metal floating on top.
Our name for the element is derived from the Anglo-Saxon for silver, ‘seolfor,’ which itself comes from ancient Germanic ‘silabar.’
Silver’s chemical symbol, Ag, is an abbreviation of the Latin word for silver, ‘argentum.’ The Latin word originates from argunas, a Sanskrit word meaning shining.
The historical association between silver and money is still found in some languages. The French word for silver is argent, and the same word is used for money. The Romans used the word ‘argentarius’ to mean banker (silver trader).
Discovery of Zinc
Zinc ores have been used to make brass (a mixture of copper and zinc) and other alloys since ancient times.
A zinc alloy comprising 87.5% zinc was discovered in an ancient site in Transylvania.
Zinc smelting began in the 12th century in India by reducing calamine (zinc carbonate, ZnCO3) with wool and other organic materials.
The element name is reported to come from the old German word ‘zinke’ meaning pointed; a reference to the sharp pointed crystals formed after smelting.
Credit for isolating the metal is usually given to Andreas Marggraf in 1746, in Berlin. He heated a mixture of calamine ore and carbon in a closed vessel without copper to produce the metal.
Discovery of Nickel
Nickel is present in metallic meteorites and so has been in use since ancient times.
Artifacts made from metallic meteorites have been found dating from as early as 5000 BC – for example beads in graves in Egypt
Iron is the most abundant element in metallic meteorites, followed by nickel.
It was not until the 1750s that nickel was discovered to be an element.
In the 1600s, a dark red ore, often with a green coating, had been a source of irritation for copper miners in Saxony, Germany. They believed the dark red substance was an ore of copper, but they had been unable to extract any copper from it.
In frustration, they had named it ‘kupfernickel’ which could be translated as ‘goblin’s copper’ because clearly, from the miners’ point of view at any rate, there were goblins or little imps at work, preventing them extracting the copper.
Between 1751 and 1754, the Swedish chemist Axel Cronstedt carried out a number of experiments to determine the true nature of kupfernickel. (We now know that kupfernickel is nickel arsenide, NiAs.)
After finding that its chemical reactions were not what he would have expected from a copper compound, he heated kupfernickel with charcoal to yield a hard, white metal, whose color alone showed it could not be copper. Its properties, including its magnetism, led him to conclude that he had isolated a new metallic element.
Cronstedt named the new element nickel, after the kupfernickel from which he had isolated it.
There is a satisfying symmetry in this discovery. Cronstedt was a pupil of George Brandt, who had discovered cobalt, which sits immediately to the left of nickel in the periodic table.
The names of both elements have their origins in the frustrations of miners caused by metal-arsenic ores: nickel arsenide and cobalt arsenide. Cobalt’s name is derived from the German ‘kobold’ meaning ‘goblin’ – a close relative of the creature from which nickel’s name was derived.
In cobalt’s case, miners mistakenly thought the ore contained silver, and called the ore kobold in frustration at the wicked goblins who they believed were preventing them getting silver from the ore.
In the early twentieth century, Ludwig Mond patented a process using nickel carbonyl to purify nickel. This process is still used today.
Discovery of Cobalt
Since ancient times cobalt compounds have been used to produce blue glass and ceramics.
The element was first isolated by Swedish chemist George Brandt in 1735. He showed it was the presence of the element cobalt that caused the blue color in glass, not bismuth as previously thought.
In about 1741 he wrote, “As there are six kinds of metals, so I have also shown with reliable experiments… that there are also six kinds of half-metals: a new half-metal, namely cobalt regulus in addition to mercury, bismuth, zinc, and the reguluses of antimony and arsenic.”
The word cobalt is derived from the German ‘kobold’, meaning goblin or elf.
Discovery of Iron
Iron has been known since ancient times.
The first iron used by humans is likely to have come from meteorites.
Most objects that fall to earth from space are stony, but a small proportion, such as the one pictured, are ‘iron meteorites’ with iron contents of over 90 percent.
Iron corrodes easily, so iron artifacts from ancient times are much rarer that objects made of silver or gold. This makes it harder to trace the history of iron than the less reactive metals.
Artifacts made from meteorite iron have been found dating from about 5000 BC (and so are about 7000 years old) – for example iron beads in graves in Egypt.
In Mesopotamia (Iraq) there is evidence people were smelting iron around 5000 BC.
Artifacts made of smelted iron have been found dating from about 3000 BC in Egypt and Mesopotamia.
In those times, iron was a ceremonial metal; it was too expensive to be used in everyday life. Assyrian writings tell us that iron was eight times more valuable than gold.
The iron age began about 1300-1200 BC when iron became cheap enough to replace bronze.
Adding carbon to iron to make steel was probably accidental at first – a coming together of molten iron and charcoal from the smelting fire. This probably happened about 1000 BC. Until this happened there were few technological reasons for the bronze age to give way to the iron age; the techniques of improving iron by adding carbon (to make steel) and coldworking were needed before iron would be wholly preferred to bronze.
Iron was used commonly in Roman times. In the first century Pliny the Elder said, “It is by the aid of iron that we construct houses, cleave rocks, and perform so many other useful offices in life.”
The origin of the chemical symbol Fe is from the Latin word ‘ferrum’ meaning iron. The word iron itself comes from ‘iren’ in Anglo-Saxon.
Discovery of Chromium
Chromium was discovered in 1780 by French chemist Nicolas Louis Vauquelin in Paris. He discovered the element in a mineral sample of ‘Siberian red lead’- now known as crocoite (lead chromate).
He boiled the crushed mineral with potassium carbonate to produce lead carbonate and a yellow potassium salt solution of chromic acid.
Vauquelin was convinced by further experiments on the solution that he had found a new metal.
In 1781 he succeeded in isolating the metal. Initially he removed the lead from the mineral sample by precipitation with hydrochloric acid. Vauquelin then obtained the oxide by evaporation and finally isolated chromium by heating the oxide in a charcoal oven.
Vauquelin also identified small amounts of chromium in ruby and emerald stones.
Vauquelin went on to discover Beryllium in 1798.
Chromium was named from the Greek word ‘chroma’, meaning color because it forms a variety of colorful compounds.
Discovery of Titanium
Titanium’s discovery was announced in 1791 by the amateur geologist Reverend William Gregor from Cornwall, England.
Gregor found a black, magnetic sand that looked like gunpowder in a stream in the parish of Mannacan in Cornwall, England. (We now call this sand ilmenite; it is a mixture consisting mainly of the oxides of iron and titanium.)
Gregor analyzed the sand, finding it was largely magnetite (Fe3O4) and the rather impure oxide of a new metal, which he described as ‘reddish brown calx.’
This calx turned yellow when dissolved in sulfuric acid and purple when reduced with iron, tin or zinc. Gregor concluded that he was dealing with a new metal, which he named manaccanite in honor of the parish of Mannacan.
Having discovered a new metal, Gregor returned to his pastoral duties.
Little more happens in our story until 1795, when the well-known German chemist Martin Klaproth experienced the thrill of discovering a new metallic element. Klaproth called the new metal titanium, after the Titans, the sons of the Earth goddess in Greek mythology.
Klaproth discovered titanium in the mineral rutile, from Boinik, Hungary. Just like Gregor’s calx, the rutile was a red color. In 1797 Klaproth read Gregor’s account from 1791 and realized that the red oxide in which he had found titanium and the red oxide in which Gregor had found manaccanite were in fact the same; titanium and maccanite were the same element and Gregor was the element’s true discoverer.
Gregor may have beaten Klaproth to the new metal, but scientists preferred Klaproth’s ‘titanium’ to Gregor’s ‘manaccanite.’
Obtaining a sample of pure titanium proved to be much harder than discovering it.
Many scientists tried, but it took 119 years from its discovery until 99.9% pure titanium was isolated in 1910 by metallurgist Matthew Hunter in Schenectady, New York, who heated titanium (IV) chloride with sodium to red-heat in a pressure cylinder.
In 1936, the Kroll Process (heating titanium (IV) chloride with magnesium) made the commercial production of titanium possible. By 1948 worldwide production had reached just 3 tons a year.
By 1956, however, scientists and engineers had realized titanium’s properties were highly desirable and worldwide production had exploded to 25,000 tons a year.
The 2011 forecast for worldwide production of titanium metal using the Kroll process was 223,000 metric tons.
Discovery of Magnesium
Magnesium and calcium were once thought to be the same substance. In 1755 Scottish chemist Joseph Black showed by experiment that the two were different. Black wrote:
“We have already shewn by experiment, that magnesia alba [magnesium carbonate] is a compound of a peculiar earth and fixed air.”
Magnesium was first isolated by Sir Humphrey Davy in 1808, in London, England. Davy had built a large battery and used it to pass electricity through salts. In doing so, he discovered or isolated for the first time several alkali and alkali earth metals.
In magnesium’s case, Davy’s method was similar to the one he used for barium, calcium and strontium.
Davy made a paste of moist magnesium oxide and red mercury oxide. )
He made a depression in the paste and placed about 3.5 grams of mercury metal there to act as the negative electrode. He used platinum as the positive electrode. Davy did the experiment under naphtha (a liquid hydrocarbon under which he had found he could safely store potassium and sodium).
When electricity was passed through the paste, a magnesium-mercury amalgam formed at the mercury electrode. (In later experiments Davy used moist magnesium sulfate instead of the oxide and obtained the amalgam much faster.)
The mercury was then removed from the amalgam by heating to leave magnesium metal.
In a lecture to the Royal Society in June 1808, Davy described how the magnesium he obtained was not pure because of difficulties in removing the mercury entirely from the magnesium. He was, however, able to observe that in air the metal turned into a white powder, gaining weight as it reacted with oxygen and returned to its oxide form.
Davy thought the logical name for the new metal was ‘magnesium’ but instead called it ‘magnium.’
He thought the name ‘magnium’ was, “objectionable, but magnesium has been already applied to metallic manganese…”
By 1812, Davy had changed his mind, following the “candid criticisms of some philosophical friends,” and the new metal became known as magnesium, while metallic manganese became known as… manganese.
Magnesium’s name is derived from magnesia, which Davy used in his experiment. Magnesia is the district of Thessaly in Greece where magnesia alba [magnesium carbonate] was found.
In France, in 1830, Antoine Bussy published his work showing how pure magnesium metal could be obtained. Bussy had read Friedrich Wöhler’s 1828 publication of how he had produced pure aluminum by reacting aluminum chloride with potassium. By analogy, Bussy thought he could do something similar to produce pure magnesium from magnesium chloride; he was correct.
Under red heat he reacted magnesium chloride with potassium vapor and obtained pure magnesium. He wrote, “The metal is silvery white, very brilliant, very malleable, flattens into flakes under a hammer… dilute acids attack the metal, releasing hydrogen.”
Discovery of Calcium
People have used calcium’s compounds for thousands of years – in cement, for example.
Limestone [calcium carbonate] was called calx by the Romans. The Romans heated calx, driving off carbon dioxide to leave calcium oxide. To make cement, all you have to do is mix calcium oxide with water. The Romans built vast amphitheaters and aqueducts using calcium oxide cement to bond stones together.
Despite the long history of calcium’s compounds, the element itself was not discovered until electricity was available for use in experiments.
Calcium was first isolated by Sir Humphry Davy in 1808 in London. In a lecture to the Royal Society in June 1808, Davy described his experiments that year, which produced tiny amounts of metal, at best. He could not find any way to produce more calcium metal until a letter from Jöns Berzelius in Stockholm pointed him in the right direction.
Davy learned that Berzelius and Magnus Pontin had used a battery to decompose calcium oxide at a mercury electrode and they had obtained an amalgam of mercury and calcium. (Berzelius, the great Swedish chemist, exchanged a great deal of information with Davy. Berzelius had earlier learned from Davy that potassium could be dissolved in mercury to form an amalgam. Berzelius had extended the method.)
Davy made a paste of slaked lime [calcium oxide, slightly moistened to form calcium hydroxide] and red oxide ofmercury [mercury (II) oxide].
He made a depression in the paste and placed about 3.5 grams of mercury metal there to act as an electrode. Platinum was used as the counter electrode. Davy carried out the experiment under naptha (a liquid hydrocarbon under which he had found he could safely store potassium and sodium).
When electricity was passed through the paste, a calcium-mercury amalgam formed at the mercury electrode.
Davy removed the mercury by distillation to reveal a new element: calcium.
Davy used the same procedure to isolate strontium,barium, and magnesium.
He named the metal calcium because of its occurrence in calx.
Discovery of Potassium
In 1806 English chemist Sir Humphry Davy discovered that chemical bonding was electrical in nature and that he could use electricity to split substances into their basic building blocks – the chemical elements.
In 1807 he isolated potassium for the first time at the Royal Institution, London. He electrolyzed dried potassium hydroxide (potash) which he had very slightly moistened by exposing it to the moist air in his laboratory. The electrolysis was powered by the combined output of three large batteries he had built.
When he applied a voltage from his batteries to the potassium hydroxide, he found globules “having a high metallic lustre” collected at the negatively charged electrode.
Edmund Davy, who assisted in the experiment, described Sir Humphry Davy’s reaction to the production of potassium metal, his Eureka moment:
“… when the minute globules of potassium burst through the crust of potash, and take fire as they entered the atmosphere, he could not contain his joy – he actually danced about the room in ecstatic delight; some little time was required for him to compose himself sufficiently to continue the experiment.”
Potassium was the first metal to be isolated by electrolysis.
Davy was astonished at the new metal’s low density, observing that it floated on oil – something no other metal would do. He placed a piece of potassium in water and observed that the water, “decomposes it with great violence, an instantaneous explosion with brilliant flame. He also (bravely) added potassium to hydrochloric acid and saw it burn with a bright red flame.
The name potassium is from the English word ‘potash’, originally meaning an alkali extracted with water in a pot of ash of burned wood or tree leaves.
Potassium’s symbol K comes from ‘kalium’ the name of the element in Germany and Scandinavia.
Just a few days after isolating potassium, Davy isolatedsodium for the first time using the same method.
Discovery of Lithium
Lithium was discovered by Johan Arfvedson in 1817 in Stockholm, Sweden, during an analysis of petalite (LiAlSi4O10).
He found the petalite contained “silica, alumina and an alkali.” (1)
The new alkali metal in the petalite had unique properties.
It required more acid to neutralize it than sodium and its carbonate was only sparingly soluble in water – unlike sodium carbonate.
The new alkali differed from potassium because it did not give a precipitate with tartaric acid.
Arfvedson tried to produce a pure sample of the new metal by electrolysis, but he was unsuccessful; the battery he used was not powerful enough. (2)
The pure metal was isolated the following year by both Swedish chemist William Brande and English chemist Humphry Davy working independently.
Davy obtained a small quantity of lithium metal by electrolysis of lithium carbonate. (3)
He noted the new element had a red flame color somewhat like strontium and produced an alkali solution when dissolved in water.
In days less safety-conscious than the present, Brande said of lithium, “its solution tastes acrid like the other fixed alkalies.” (4)
By 1855 Robert Bunsen and Augustus Matthiessen were independently producing the metal in large quantities by electrolysis of molten lithium chloride.
Lithium’s name is derived from the Greek word ‘lithos’ meaning, ‘stone.’
Discovery of Carbon
Carbon has been known since ancient times in the form of soot, charcoal, graphite and diamonds. Ancient cultures did not realize, of course, that these substances were different forms of the same element
French scientist Antoine Lavoisier named carbon and he carried out a variety of experiments to reveal its nature.
In 1772 he pooled resources with other chemists to buy a diamond, which they placed in a closed glass jar. They focused the sun’s rays on the diamond with a remarkable giant magnifying glass and saw the diamond burn and disappear.
Lavoisier noted the overall weight of the jar was unchanged and that when it burned, the diamond had combined with oxygen to form carbon dioxide. He concluded that diamond and charcoal were made of the same element – carbon.
In 1779, Swedish scientist Carl Scheele showed that graphite burned to form carbon dioxide and so must be another form of carbon.
In 1796, English chemist Smithson Tennant established that diamond was pure carbon and not a compound of carbon; it burned to form only carbon dioxide.
Tennant also proved that when equal weights of charcoal and diamonds were burned, they produced the same amount of carbon dioxide.
In 1855, English chemist Benjamin Brodie produced pure graphite from carbon, proving graphite was a form of carbon
Although it had been previously attempted without success, in 1955 American scientist Francis Bundy and coworkers at General Electric finally demonstrated that graphite could be transformed into diamond at high temperature and high pressure.
In 1985, Robert Curl, Harry Kroto and Richard Smalley discovered fullerenes, a new form of carbon in which the atoms are arranged in soccer-ball shapes. The best known fullerene is buckminsterfullerene, also known as C60, consisting of 60 carbon atoms. A large family of fullerenes exists, starting at C20 and reaching up to C540.
The most recently discovered allotrope of carbon is graphene, which consists of a single layer of carbon atoms arranged in hexagons. If these layers were stacked upon one other, graphite would be the result. Graphene has a thickness of just one atom.
Graphene’s discovery was announced in 2004 by Kostya Novoselov and Andre Geim, who used adhesive tape to detach a single layer of atoms from graphite to produce the new allotrope.
Discovery of Oxygen
Oxygen was discovered in 1774 by Joseph Priestley in England and two years earlier, but unpublished, by Carl W. Scheele in Sweden.
Scheele heated several compounds including potassium nitrate, manganese oxide, and mercury oxide and found they released a gas which enhanced combustion.
Priestley heated mercury oxide, focusing sunlight using a 12-inch ‘burning lens’ – a very large magnifying glass – to bring the oxide to a high temperature. Priestley’s lens was smaller than the enormous one used by Antoine Lavoisier in his investigation of carbon. (Shown on Chemicool’s carbon page.)
Totally unexpectedly, the hot mercury oxide yielded a gas that made a candle burn five times faster than normal. Priestley wrote: “But what surprised me more than I can well express was that a candle burned in this air with a remarkably vigorous flame. I was utterly at a loss how to account for it.” )
In addition to noticing the effect of oxygen on combustion, Priestley later noted the new gas’s biological role. He placed a mouse in a jar of oxygen, expecting it would survive for 15 minutes maximum before it suffocated. Instead, the mouse survived for a whole hour and was none the worse for it.)
Antoine Lavoisier carried out similar experiments to Priestley’s and added to our knowledge enormously by discovering that air contains about 20 percent oxygen and that when any substance burns, it actually combines chemically with oxygen.
Lavoisier also found that the weight of the gas released by heating mercury oxide was identical to the weight lost by the mercury oxide, and that when other elements react with oxygen their weight gain is identical to the weight lost from the air.
This enabled Lavoisier to state a new fundamental law: the law of the conservation of matter; “matter is conserved in chemical reactions” or, alternatively, “the total mass of a chemical reaction’s products is identical to the total mass of the starting materials.”
In addition to these achievements, it was Lavoisier who first gave the element its name oxygen.
The word oxygen is derived from the Greek words ‘oxys’ meaning acid and ‘genes’ meaning forming.
Before it was discovered and isolated, a number of scientists had recognized the existence of a substance with the properties of oxygen:
In the early 1500s Leonardo da Vinci observed that a fraction of air is consumed in respiration and combustion.
In 1665 Robert Hooke noted that air contains a substance which is present in potassium nitrate [potassium nitrate releases oxygen when heated,] and a larger quantity of an unreactive substance [which we call nitrogen].
In 1668 John Mayow wrote that air contains the gas oxygen [he called it nitroarial spirit], which is consumed in respiration and burning.
Mayow observed that: substances do not burn in air from which oxygen is absent; oxygen is present in the acid part of potassium nitrate [i.e., in the nitrate - he was right!]; animals absorb oxygen into their blood when they breathe; air breathed out by animals has less oxygen in it than fresh air.
Discovery of Hydrogen
A favorite school chemistry experiment is to add a metal such as magnesium to an acid. The metal reacts with the acid, forming a salt and releases hydrogen from the acid. The hydrogen gas bubbles up from the liquid and students collect it in small quantities for further experiments, such as the ‘pop-test.’
The first recorded instance of hydrogen made by human action was in the first half of the 1500s, by a similar method to that used in schools now. Theophrastus Paracelsus, a physician, dissolved iron in sulfuric acid and observed the release of a gas. He is reported to have said of the experiment, “Air arises and breaks forth like a wind.” He did not, however, discover any of hydrogen’s properties.
Turquet De Mayerne repeated Paracelsus’s experiment in 1650 and found that the gas was flammable. Neither Paracelsus nor De Mayerne proposed that hydrogen could be a new element. Indeed, Paracelsus believed there were only three elements – the tria prima – salt, sulfur, and mercury – and that all other substances were made of different combinations of these three. (Chemistry still had a long way to go!)
In 1670, English scientist Robert Boyle added iron to sulfuric acid. He showed the resulting (hydrogen) gas only burned if air was present and that a fraction of the air (we would now call it oxygen) was consumed by the burning.
Hydrogen was first recognized as a distinct element in 1766 by English scientist Henry Cavendish, when he prepared it by reacting hydrochloric acid with zinc. He described hydrogen as “inflammable air from metals” and established that it was the same material (by its reactions and its density) regardless of which metal and which acid he used to produce it.(1) Cavendish also observed that when the substance was burned, it produced water.
French scientist Antoine Lavoisier later named the element hydrogen (1783). The name comes from the Greek ‘hydro’ meaning water and ‘genes’ meaning forming – hydrogen is one of the two water forming elements.
In 1806, with hydrogen well-established as an element, English chemist Humphry Davy pushed a strong electric current through purified water.
He found hydrogen and oxygen were formed. The experiment demonstrated that electricity could pull substances apart into their constituent elements. Davy realized that substances were bound together by an electrical phenomenon; he had discovered the true nature of chemical bonding.
حال ساده:Simple present tense
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