Hydrogen (H)

In the early 1500s the alchemist Paracelsus noted that the bubbles given off when iron filings were added to sulfuric acid were flammable. In 1671 Robert Boyle made the same observation. Neither followed up their discovery of hydrogen, and so Henry Cavendish gets the credit. In 1766 he collected the bubbles and showed that they were different from other gases. He later showed that when hydrogen burns it forms water, thereby ending the belief that water was an element. The gas was given its name hydro-gen, meaning water-former, by Antoine Lavoisier.

Helium (He)

In 1868, Pierre J. C. Janssen travelled to India to measure the solar spectrum during a total eclipse and observed a new yellow line which indicated a new element. Joseph Norman Lockyer recorded the same line by observing the sun through London smog and, assuming the new element to be a metal, he named it helium. In 1882, the Italian Luigi Palmieri found the same line the spectrum of gases emitted by Vesuvius, as did the American William Hillebrand in 1889 when he collected the gas given off by the mineral uraninite (UO₂) as it dissolves in acid. However, it was Per Teodor Cleve and Nils Abraham Langer at Uppsala, Sweden, in 1895, who repeated that experiment and confirmed it was helium and measured its atomic weight.

Lithium (Li)

The first lithium mineral petalite, LiAlSi₄O₁₀, was discovered on the Swedish island of Utö by the Brazilian, Jozé Bonifácio de Andralda e Silva in the 1790s. It was observed to give an intense crimson flame when thrown onto a fire. In 1817, Johan August Arfvedson of Stockholm analysed it and deduced it contained a previously unknown metal, which he called lithium. He realised this was a new alkali metal and a lighter version of sodium. However, unlike sodium he was not able to separate it by electrolysis. In 1821 William Brande obtained a tiny amount this way but not enough on which to make measurements. It was not until 1855 that the German chemist Robert Bunsen and the British chemist Augustus Matthiessen obtained it in bulk by the electrolysis of molten lithium chloride.

Beryllium (Be)

The gemstones beryl and emerald are both forms of beryllium aluminium silicate, BeAl₂(SiO₃)₆. The French mineralogist Abbé René-Just Haüy thought they might harbour a new element, and he asked Nicholas Louis Vauquelin, to analyse them and he realised they harboured a new metal and he investigated it. In February 1798 Vauquelin announced his discovery at the French Academy and named the element glaucinium (Greek glykys = sweet) because its compounds tasted sweet. Others preferred the name beryllium, based on the gemstone, and this is now the official name. Beryllium metal was isolated in 1828 by Friedrich Wöhler at Berlin and independently by Antoine-Alexandere-Brutus Bussy at Paris, both of whom extracted it from beryllium chloride (BeCl₂) by reacting this with potassium.

Boron (B)

For centuries the only source of borax, Na₂B₂O₅(OH)₄, was the crystallized deposits of Lake Yamdok Cho, in Tibet. It was used as a flux used by goldsmiths. In 1808, Louis-Josef Gay-Lussac and Louis-Jacques Thénard working in Paris, and Sir Humphry Davy in London, independently extracted boron by heating borax with potassium metal. In fact, neither had produced the pure element which is almost impossible to obtain. A purer type of boron was isolated in 1892 by Henri Moissan. Eventually, E. Weintraub in the USA produced totally pure boron by sparking a mixture of boron chloride, BCl₃ vapour, and hydrogen. The material so obtained boron was found to have very different properties to those previously reported.

Carbon (C)

Carbon occurs naturally as anthracite (a type of coal), graphite, and diamond. More readily available historically was soot or charcoal. Ultimately these various materials were recognised as forms of the same element. Not surprisingly, diamond posed the greatest difficulty of identification. Naturalist Giuseppe Averani and medic Cipriano Targioni of Florence were the first to discover that diamonds could be destroyed by heating. In 1694 they focussed sunlight on to a diamond using a large magnifying glass and the gem eventually disappeared. Pierre-Joseph Macquer and Godefroy de Villetaneuse repeated the experiment in 1771. Then, in 1796, the English chemist Smithson Tennant finally proved that diamond was just a form of carbon by showing that as it burned it formed only CO₂

Nitrogen (N)

Nitrogen in the form of ammonium chloride, NH₄Cl, was known to the alchemists as sal ammonia. It was manufactured in Egypt by heating a mixture of dung, salt and urine. Nitrogen gas itself was obtained in the 1760s by both Henry Cavendish and Joseph Priestley and they did this by removing the oxygen from air. They noted it extinguished a lighted candle and that a mouse breathing it would soon die. Neither man deduced that it was an element. The first person to suggest this was a young student Daniel Rutherford in his doctorate thesis of September 1772 at Edinburgh, Scotland.

Oxygen (O)

In 1608, Cornelius Drebbel had shown that heating saltpetre (potassium nitrate, KNO₃) released a gas. This was oxygen although it was not identified as such. The credit for discovering oxygen is now shared by three chemists: an Englishman, a Swede, and a Frenchman. Joseph Priestley was the first to publish an account of oxygen, having made it in 1774 by focussing sunlight on to mercuric oxide (HgO), and collecting the gas which came off. He noted that a candle burned more brightly in it and that it made breathing easier. Unknown to Priestly, Carl Wilhelm Scheele had produced oxygen in June 1771. He had written an account of his discovery but it was not published until 1777. Antoine Lavoisier also claimed to have discovered oxygen, and he proposed that the new gas be called oxy-gène, meaning acid-forming, because he thought it was the basis of all acids.

Fluorine (F)

The early chemists were aware that metal fluorides contained an unidentified element similar to chlorine, but they could not isolate it. (The French scientist, André Ampère coined the name fluorine in 1812.) Even the great Humphry Davy was unable to produce the element, and he became ill by trying to isolate it from hydrofluoric acid. The British chemist George Gore in 1869 passed an electric current through liquid HF but found that the gas which was liberated reacted violently with his apparatus. He thought it was fluorine but was unable to collect it and prove it. Then in 1886 the French chemist Henri Moissan obtained it by the electrolysis of potassium bifluoride (KHF2) dissolved in liquid HF.

Neon (N)

In 1898, William Ramsay and Morris Travers at University College London isolated krypton gas by evaporating liquid argon. They had been expecting to find a lighter gas which would fit a niche above argon in the periodic table of the elements. They then repeated their experiment, this time allowing solid argon to evaporate slowly under reduced pressure and collected the gas which came off first. This time they were successful, and when they put a sample of the new gas into their atomic spectrometer it startled them by the brilliant red glow that we now associate with neon signs. Ramsay named the new gas neon, basing it on neos, the Greek word for new.

Sodium (Na)

Salt (sodium chloride, NaCl) and soda (sodium carbonate, Na2CO3) had been known since prehistoric times, the former used as a flavouring and preservative, and the latter for glass manufacture. Salt came from seawater, while soda came from the Natron Valley in Egypt or from the ash of certain plants. Their composition was debated by early chemists and the solution finally came from the Royal Institution in London in October 1807 where Humphry Davy exposed caustic soda (sodium hydroxide, NaOH) to an electric current and obtained globules of sodium metal, just as he had previously done for potassium, although he needed to use a stronger current. The following year, Louis-Josef Gay-Lussac and Louis-Jacques Thénard obtained sodium by heating to red heat a mixture of caustic soda and iron filings.

Magnesium (Mg)

The first person to recognise that magnesium was an element was Joseph Black at Edinburgh in 1755. He distinguished magnesia (magnesium oxide, MgO) from lime (calcium oxide, CaO) although both were produced by heating similar kinds of carbonate rocks, magnesite and limestone respectively. Another magnesium mineral called meerschaum (magnesium silicate) was reported by Thomas Henry in 1789, who said that it was much used in Turkey to make pipes for smoking tobacco. An impure form of metallic magnesium was first produced in 1792 by Anton Rupprecht who heated magnesia with charcoal. A pure, but tiny, amount of the metal was isolated in 1808 by Humphry Davy by the electrolysis of magnesium oxide. However, it was the French scientist, Antoine-Alexandre-Brutus Bussy who made a sizeable amount of the metal in 1831 by reacting magnesium chloride with potassium, and he then studied its properties.

Aluminium (Al)

The analysis of a curious metal ornament found in the tomb of Chou-Chu, a military leader in 3rd century China, turned out to be 85% aluminium. How it was produced remains a mystery. By the end of the 1700s, aluminium oxide was known to contain a metal, but it defeated all attempts to extract it. Humphry Davy had used electric current to extract sodium and potassium from their so-called 'earths' (oxides), but his method did not release aluminium in the same way. The first person to produce it was Hans Christian Oersted at Copenhagen, Denmark, in 1825, and he did it by heating aluminium chloride with potassium. Even so, his sample was impure. It fell to the German chemist Friedrich Wöhler to perfect the method in 1827, and obtain pure aluminium for the first time by using sodium instead of potassium.

Silicon (Si)

Silica (SiO₂) in the form of sharp flints were among the first tools made by humans. The ancient civilizations used other forms of silica such as rock crystal, and knew how to turn sand into glass. Considering silicon's abundance, it is somewhat surprising that it aroused little curiosity among early chemists. Attempts to reduce silica to its components by electrolysis had failed. In 1811, Joseph Gay Lussac and Louis Jacques Thénard reacted silicon tetrachloride with potassium metal and produced some very impure form of silicon. The credit for discovering silicon really goes to the Swedish chemist Jöns Jacob Berzelius of Stockholm who, in 1824, obtained silicon by heating potassium fluorosilicate with potassium. The product was contaminated with potassium silicide, but he removed this by stirring it with water, with which it reacts, and thereby obtained relatively pure silicon powder.

Phosphorus (P)

Phosphorus was first made by Hennig Brandt at Hamburg in 1669 when he evaporated urine and heated the residue until it was red hot, whereupon phosphorus vapour distilled which he collected by condensing it in water. Brandt kept his discovery secret, thinking he had discovered the Philosopher's Stone that could turn base metals into gold. When he ran out of money, he sold phosphorus to Daniel Kraft who exhibited it around Europe including London where Robert Boyle was fascinated by it. He discovered how it was produced and investigated it systematically, (his assistant Ambrose Godfrey set up his own business making and selling phosphorus and became rich). When it was realised that bone was calcium phosphate, and could be used to make phosphorus, and it became more widely available. Demand from match manufacturers in the 1800s ensured a ready market.

Sulfur (S)

Sulfur is mentioned 15 times in the Bible, and was best known for destroying Sodom and Gomorrah. It was also known to the ancient Greeks, and burnt as a fumigant. Sulfur was mined near Mount Etna in Sicily and used for bleaching cloth and preserving wine, both of which involved burning it to form sulfur dioxide, and allowing this to be absorbed by wet clothes or the grape juice. For centuries, sulfur along with mercury and salt, was believed to be a component of all metals and formed the basis of alchemy whereby one metal could be transmuted into another. Antoine Lavoisier thought that sulfur was an element, but in 1808 Humphry Davy said it contained hydrogen. However, his sample was impure and when Louis-Josef Gay-Lussac and Louis-Jacques Thénard proved it to be an element the following year, Davy eventually agreed.

Chlorine (Cl)

Hydrochloric acid (HCl) was known to the alchemists. The gaseous element itself was first produced in 1774 by Carl Wilhelm Scheele at Uppsala, Sweden, by heating hydrochloric acid with the mineral pyrolusite which is naturally occurring manganese dioxide, MnO2. A dense, greenish-yellow gas was evolved which he recorded as having a choking smell and which dissolved in water to give an acid solution. He noted that it bleached litmus paper, and decolorized leaves and flowers. Humphry Davy investigated it in 1807 and eventually concluded not only that it was a simple substance, but that it was truly an element. He announced this in 1810 and yet it took another ten years for some chemists finally to accept that chlorine really was an element.

Argon (Ar)

Although argon is abundant in the Earth's atmosphere, it evaded discovery until 1894 when Lord Rayleigh and William Ramsay first separated it from liquid air. In fact the gas had been isolated in 1785 by Henry Cavendish who had noted that about 1% of air would not react even under the most extreme conditions. That 1% was argon. Argon was discovered as a result of trying to explain why the density of nitrogen extracted from air differed from that obtained by the decomposition of ammonia. Ramsay removed all the nitrogen from the gas he had extracted from air, and did this by reacting it with hot magnesium, forming the solid magnesium nitride. He was then left with a gas that would not react and when he examined its spectrum he saw new groups of red and green lines, confirming that it was a new element.

Potassium (k)

Potassium salts in the form of saltpetre (potassium nitrate, KNO₃), alum (potassium aluminium sulfate, KAl(SO₄)₂), and potash (potassium carbonate, K₂CO₃) have been known for centuries. They were used in gunpowder, dyeing, and soap making. They were scraped from the walls of latrines, manufactured from clay and sulfuric acid, and collected as wood ash respectively. Reducing them to the element defeated the early chemists and potassium was classed as an 'earth' by Antoine Lavoisier. Then in 1807, Humphry Davy exposed moist potash to an electric current and observed the formation of metallic globules of a new metal, potassium. He noted that when they were dropped into water they skimmed around on the surface, burning with a lavender-coloured flame.

Calcium (Ca)

Lime (calcium oxide, CaO) was the useful material obtained by heating limestone and used for centuries to make plaster and mortar. Antoine Lavoisier classified it as an 'earth' because it seemed impossible to reduce it further, but he suspected it was the oxide of an unknown element. In 1808, Humphry Davy tried to reduce moist lime by electrolysis, just as he had done with sodium and potassium, but he was not successful. So he tried a mixture of lime and mercury oxide and while this produced an amalgam of calcium and mercury, it was not enough to confirm that he'd obtained a new element. (Jöns Jacob Berzelius had conducted a similar experiment and also obtained the amalgam.) Davy tried using more lime in the mixture and produced more of the amalgam from which he distilled off the mercury leaving just calcium.

References

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