The United Kingdom the United Kingdom of Great Britain and Northern Ireland, sometimes referred to as Britain, is a sovereign country located off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland, many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state, the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world; the Irish Sea lies between Great Ireland. With an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world, it is the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017. The UK is constitutional monarchy; the current monarch is Queen Elizabeth II, who has reigned since 1952, making her the longest-serving current head of state.
The United Kingdom's capital and largest city is London, a global city and financial centre with an urban area population of 10.3 million. Other major urban areas in the UK include Greater Manchester, the West Midlands and West Yorkshire conurbations, Greater Glasgow and the Liverpool Built-up Area; the United Kingdom consists of four constituent countries: England, Scotland and Northern Ireland. Their capitals are London, Edinburgh and Belfast, respectively. Apart from England, the countries have their own devolved governments, each with varying powers, but such power is delegated by the Parliament of the United Kingdom, which may enact laws unilaterally altering or abolishing devolution; the nearby Isle of Man, Bailiwick of Guernsey and Bailiwick of Jersey are not part of the UK, being Crown dependencies with the British Government responsible for defence and international representation. The medieval conquest and subsequent annexation of Wales by the Kingdom of England, followed by the union between England and Scotland in 1707 to form the Kingdom of Great Britain, the union in 1801 of Great Britain with the Kingdom of Ireland created the United Kingdom of Great Britain and Ireland.
Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain and Northern Ireland. There are fourteen British Overseas Territories, the remnants of the British Empire which, at its height in the 1920s, encompassed a quarter of the world's land mass and was the largest empire in history. British influence can be observed in the language and political systems of many of its former colonies; the United Kingdom is a developed country and has the world's fifth-largest economy by nominal GDP and ninth-largest economy by purchasing power parity. It has a high-income economy and has a high Human Development Index rating, ranking 14th in the world, it was the world's first industrialised country and the world's foremost power during the 19th and early 20th centuries. The UK remains a great power, with considerable economic, military and political influence internationally, it is sixth in military expenditure in the world. It has been a permanent member of the United Nations Security Council since its first session in 1946.
It has been a leading member state of the European Union and its predecessor, the European Economic Community, since 1973. The United Kingdom is a member of the Commonwealth of Nations, the Council of Europe, the G7, the G20, NATO, the Organisation for Economic Co-operation and Development and the World Trade Organization; the 1707 Acts of Union declared that the kingdoms of England and Scotland were "United into One Kingdom by the Name of Great Britain". The term "United Kingdom" has been used as a description for the former kingdom of Great Britain, although its official name from 1707 to 1800 was "Great Britain"; the Acts of Union 1800 united the kingdom of Great Britain and the kingdom of Ireland in 1801, forming the United Kingdom of Great Britain and Ireland. Following the partition of Ireland and the independence of the Irish Free State in 1922, which left Northern Ireland as the only part of the island of Ireland within the United Kingdom, the name was changed to the "United Kingdom of Great Britain and Northern Ireland".
Although the United Kingdom is a sovereign country, Scotland and Northern Ireland are widely referred to as countries. The UK Prime Minister's website has used the phrase "countries within a country" to describe the United Kingdom; some statistical summaries, such as those for the twelve NUTS 1 regions of the United Kingdom refer to Scotland and Northern Ireland as "regions". Northern Ireland is referred to as a "province". With regard to Northern Ireland, the descriptive name used "can be controversial, with the choice revealing one's political preferences"; the term "Great Britain" conventionally refers to the island of Great Britain, or politically to England and Wales in combination. However, it is sometimes used as a loose synonym for the United Kingdom as a whole; the term "Britain" is used both as a synonym for Great Britain, as a synonym for the United Kingdom. Usage is mixed, with the BBC preferring to use Britain as shorthand only for Great Britain and the UK Government, while accepting that both terms refer to the United K
Petroleum is a occurring, yellowish-black liquid found in geological formations beneath the Earth's surface. It is refined into various types of fuels. Components of petroleum are separated using a technique called fractional distillation, i.e. separation of a liquid mixture into fractions differing in boiling point by means of distillation using a fractionating column. It consists of occurring hydrocarbons of various molecular weights and may contain miscellaneous organic compounds; the name petroleum covers both occurring unprocessed crude oil and petroleum products that are made up of refined crude oil. A fossil fuel, petroleum is formed when large quantities of dead organisms zooplankton and algae, are buried underneath sedimentary rock and subjected to both intense heat and pressure. Petroleum has been recovered by oil drilling. Drilling is carried out after studies of structural geology, sedimentary basin analysis, reservoir characterisation have been completed, it is refined and separated, most by distillation, into a large number of consumer products, from gasoline and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals.
Petroleum is used in manufacturing a wide variety of materials, it is estimated that the world consumes about 95 million barrels each day. The use of petroleum as fuel is controversial due to its impact on global warming and ocean acidification. Fossil fuels, including petroleum, need to be phased out by the end of 21st century to avoid "severe and irreversable impacts for people and ecosystems", according to the UN's Intergovernmental Panel on Climate Change; the word petroleum comes from Medieval Latin petroleum, which comes from Latin petra', "rock", Latin oleum, "oil". The term was used in the treatise De Natura Fossilium, published in 1546 by the German mineralogist Georg Bauer known as Georgius Agricola. In the 19th century, the term petroleum was used to refer to mineral oils produced by distillation from mined organic solids such as cannel coal, refined oils produced from them. Petroleum, in one form or another, has been used since ancient times, is now important across society, including in economy and technology.
The rise in importance was due to the invention of the internal combustion engine, the rise in commercial aviation, the importance of petroleum to industrial organic chemistry the synthesis of plastics, solvents and pesticides. More than 4000 years ago, according to Herodotus and Diodorus Siculus, asphalt was used in the construction of the walls and towers of Babylon. Great quantities of it were found on the banks of the river Issus, one of the tributaries of the Euphrates. Ancient Persian tablets indicate the medicinal and lighting uses of petroleum in the upper levels of their society; the use of petroleum in ancient China dates back to more than 2000 years ago. In I Ching, one of the earliest Chinese writings cites that oil in its raw state, without refining, was first discovered and used in China in the first century BCE. In addition, the Chinese were the first to use petroleum as fuel as early as the fourth century BCE. By 347 AD, oil was produced from bamboo-drilled wells in China. Crude oil was distilled by Arabic chemists, with clear descriptions given in Arabic handbooks such as those of Muhammad ibn Zakarīya Rāzi.
The streets of Baghdad were paved with tar, derived from petroleum that became accessible from natural fields in the region. In the 9th century, oil fields were exploited in the area around Azerbaijan; these fields were described by the Arab geographer Abu al-Hasan'Alī al-Mas'ūdī in the 10th century, by Marco Polo in the 13th century, who described the output of those wells as hundreds of shiploads. Arab and Persian chemists distilled crude oil in order to produce flammable products for military purposes. Through Islamic Spain, distillation became available in Western Europe by the 12th century, it has been present in Romania since the 13th century, being recorded as păcură. Early British explorers to Myanmar documented a flourishing oil extraction industry based in Yenangyaung that, in 1795, had hundreds of hand-dug wells under production. Pechelbronn is said to be the first European site where petroleum has been used; the still active Erdpechquelle, a spring where petroleum appears mixed with water has been used since 1498, notably for medical purposes.
Oil sands have been mined since the 18th century. In Wietze in lower Saxony, natural asphalt/bitumen has been explored since the 18th century. Both in Pechelbronn as in the coal industry dominated the petroleum technologies. Chemist James Young noticed a natural petroleum seepage in the Riddings colliery at Alfreton, Derbyshire from which he distilled a light thin oil suitable for use as lamp oil, at the same time obtaining a more viscous oil suitable for lubricating machinery. In 1848, Young set up a small business refining the crude oil. Young succeeded, by distilling cannel coal at a low heat, in creating a fluid resembling petroleum, which when treated in the same way as the seep oil gave similar products. Young found that by sl
National Benzole was a petroleum brand used in the United Kingdom from 1919 to the 1960s. In 1957 the National Benzole Co. became wholly owned by Shell-Mex and B. P. Ltd but continued its separate trading identity. In the early 1960s National Benzole was re-branded as National and continued trading as a UK retailer of petroleum products until the early 1990s, when the brand was phased out by parent company BP; the company was founded in February 1919 in a room next to the boiler house of the Gas Light and Coke Company in London's Horseferry Road. In the early years of the century, benzole production had been small scale. But, because it was as good at propelling shells as motor cars, production was expanded massively during World War One, and this led to something of a post-war "benzole-lake". A group of men, including Samuel Henshaw the chairman of the Staffordshire Chemical Company, reckoned there was money to be made from these surplus-to-requirements stocks. Henshaw became the first chairman of the National Benzole Company.
Although the idea of using benzole to power automobiles was not new, cars fuelled on neat benzole needed altered carburetter settings, inconvenient for owners who had used petrol and the effectiveness of neat benzole as a paint stripper raised concern about the possible effect on carburettor floats made of varnished cork – a common feature in US vehicles which at the time were being imported in greater numbers. There was concern about the variable quality and specification of the benzole, it was in the need to address these concerns regarding consistency of fuel quality, that Henshaw and his colleagues recognised their commercial opportunity. A distribution network was established consisting of a few storage depots round the country, supplied by a small fleet of used lorries with solid tyres, acquired from the War Disposals Board; these transported the fuel in war-surplus cans of 2, 4 or 50 gallons. The young company received a boost in 1920 with the award of the RAC Dewar Trophy to a Rolls-Royce 40/50 hp that completed a 10,000-mile reliability trial fuelled by National Benzole.
Problems arose in the same year from a coal strike which restricted benzole availability, increased demand in the ensuing years led to frequent shortages of coal shale from which the benzole was made. At the same time, some reckoned neat benzole was a little strong for the average engine and started to mix it with petrol; this led in 1922 to the replacement of benzole fuel with a "fifty-fifty mixture" of benzole and petroleum which addressed the supply issue and could be seen as an early example of customer responsiveness. Neat benzole continued to be marketed as an effective anti-knocking performance enhancing additive. Military service in the First World War introduced many British men to motoring for the first time: returning survivors began, where funds permitted, to purchase small motor cars or motor bikes, while others set up in business to maintain and repair the motor cars of the wealthy. Before the war motor fuel suppliers in the UK had included pharmacies, cycle shops or blacksmiths, but after the war commercial roadside garages began to appear at first.
Because garages were sparse the Automobile Association itself set up twelve strategically located filling stations, supplying fuel only to its own members and making no profit from the transactions. The AA fuel stations supplied only National Benzole, seen a patriotic fuel choice because the coal shale, the principal ingredient of benzole was domestically produced. In 1927 the AA dismantled its small chain of service stations as the growth of a commercially motivated service station network rendered them unnecessary, but by this time National Benzole was a nationally established fuel brand in the UK. During this period the company consciously "smartened up" its public face; the enthusiastic driver/ salesmen delivery drivers had been the company's sales force, touting relentlessly for new business as they made deliveries to existing customers. Ten years the head office had relocated to an upmarket location in London's Grosvenor Gardens and a sales force was recruited, equipped with Morris Cowleys painted yellow, which had become the company's colour.
The now famous 50/50 blend became a resounding success. To sustain the success, an imaginative advertising campaign was developed, in 1928, Mr Mercury – startlingly naked – leapt for the first time from the pages of the national newspapers. Mr Mercury, in National Benzole's black and chrome gold corporate colours, became one of the most powerful marketing images of this age; every service station in the 1930s had a National Benzole pump, for single-brand sites were unknown in those days. Mr Mercury's head was used as the brand's logo. At the outbreak of the Second World War, all petrol brands gave way to pool petrol. Mr Mercury returned in 1953, now more modestly attired in the advertisements, though he retained his winged helmet, National Benzole re-established itself as a market leader. Switching from neat benzole to the fifty-fifty mixture was not a complete solution to the supply issue, it reduced but did not eliminate the company's dependence on the UK coal mining cartel, while it introduced an inherent tension in the relationship with the petroleum suppliers who were major competitors for road fuel sales.
The petroleum supply issue was to some extent addressed by "buying on the high seas" whereby the company, having no oil refining capacity of its own, contracted to buy from shippers full tanker loads of refined fuel. As motoring passed from being a recreation for the leisure hours of a leisured class to a mainstream means
Gasoline, gas or petrol is a colorless petroleum-derived flammable liquid, used as a fuel in spark-ignited internal combustion engines. It consists of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. On average, a 42-U. S.-gallon barrel of crude oil yields about 19 U. S. gallons of gasoline after processing in an oil refinery, though this varies based on the crude oil assay. The characteristic of a particular gasoline blend to resist igniting too early is measured by its octane rating. Gasoline is produced in several grades of octane rating. Tetraethyl lead and other lead compounds are no longer used in most areas to increase octane rating. Other chemicals are added to gasoline to improve chemical stability and performance characteristics, control corrosiveness and provide fuel system cleaning. Gasoline may contain oxygen-containing chemicals such as ethanol, MTBE or ETBE to improve combustion. Gasoline used in internal combustion engines can have significant effects on the local environment, is a contributor to global human carbon dioxide emissions.
Gasoline can enter the environment uncombusted, both as liquid and as vapor, from leakage and handling during production and delivery. As an example of efforts to control such leakage, many underground storage tanks are required to have extensive measures in place to detect and prevent such leaks. Gasoline contains other known carcinogens. "Gasoline" is a North American word. The Oxford English Dictionary dates its first recorded use to 1863 when it was spelled "gasolene"; the term "gasoline" was first used in North America in 1864. The word is a derivation from the word "gas" and the chemical suffixes "-ol" and "-ine" or "-ene". However, the term may have been influenced by the trademark "Cazeline" or "Gazeline". On 27 November 1862, the British publisher, coffee merchant and social campaigner John Cassell placed an advertisement in The Times of London: The Patent Cazeline Oil, safe and brilliant … possesses all the requisites which have so long been desired as a means of powerful artificial light.
This is the earliest occurrence of the word to have been found. Cassell discovered that a shopkeeper in Dublin named Samuel Boyd was selling counterfeit cazeline and wrote to him to ask him to stop. Boyd did not reply and changed every ‘C’ into a ‘G’, thus coining the word "gazeline"; the name "petrol" is used in place of "gasoline" in most Commonwealth countries. "Petrol" was first used as the name of a refined petroleum product around 1870 by British wholesaler Carless, Capel & Leonard, who marketed it as a solvent. When the product found a new use as a motor fuel, Frederick Simms, an associate of Gottlieb Daimler, suggested to Carless that they register the trademark "petrol", but by this time the word was in general use inspired by the French pétrole, the registration was not allowed. Carless registered a number of alternative names for the product, but "petrol" nonetheless became the common term for the fuel in the British Commonwealth. British refiners used "motor spirit" as a generic name for the automotive fuel and "aviation spirit" for aviation gasoline.
When Carless was denied a trademark on "petrol" in the 1930s, its competitors switched to the more popular name "petrol". However, "motor spirit" had made its way into laws and regulations, so the term remains in use as a formal name for petrol; the term is used most in Nigeria, where the largest petroleum companies call their product "premium motor spirit". Although "petrol" has made inroads into Nigerian English, "premium motor spirit" remains the formal name, used in scientific publications, government reports, newspapers; the use of the word gasoline instead of petrol outside North America can be confusing. Shortening gasoline to gas, which happens causes confusion with various forms of gaseous products used as automotive fuel like compressed natural gas, liquefied natural gas and liquefied petroleum gas ). In many languages, the name is derived from benzene, such as Benzin in benzina in Italian. Argentina and Paraguay use the colloquial name nafta derived from that of the chemical naphtha.
The first internal combustion engines suitable for use in transportation applications, so-called Otto engines, were developed in Germany during the last quarter of the 19th century. The fuel for these early engines was a volatile hydrocarbon obtained from coal gas. With a boiling point near 85 °C, it was well-suited for early carburetors; the development of a "spray nozzle" carburetor enabled the use of less volatile fuels. Further improvements in engine efficiency were attempted at higher compression ratios, but early attempts were blocked by the premature explosion of fuel, known as knocking. In 1891, the Shukhov cracking process became the world's first commercial method to break down heavier hydrocarbons in crude oil to increase the percentage of lighter products compared to simple distillation; the evolution of gasoline followed the evolution of oil as the dominant source of energy in the industrializing world. Prior to World War One, Britain was the world's greatest industrial power and depended on its navy to protect the shipping of raw materials from its colonies.
Germany was industrializing and, like Britain, lacked many natural resources which had to be shipped to the home country. By the 1890s, Germany
Benzene is an organic chemical compound with the chemical formula C6H6. The benzene molecule is composed of six carbon atoms joined in a ring with one hydrogen atom attached to each; as it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is one of the elementary petrochemicals. Due to the cyclic continuous pi bond between the carbon atoms, benzene is classed as an aromatic hydrocarbon, the second -annulene, it is sometimes abbreviated PhH. Benzene is a colorless and flammable liquid with a sweet smell, is responsible for the aroma around petrol stations, it is used as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. As benzene has a high octane number, aromatic derivatives like toluene and xylene comprise up to 25% of gasoline. Benzene itself has been limited to less than 1 % in gasoline. Most non-industrial applications have been limited as well for the same reason.
The word "benzene" derives from "gum benzoin", an aromatic resin known to European pharmacists and perfumers since the 15th century as a product of southeast Asia. An acidic material was derived from benzoin by sublimation, named "flowers of benzoin", or benzoic acid; the hydrocarbon derived from benzoic acid thus acquired benzol, or benzene. Michael Faraday first isolated and identified benzene in 1825 from the oily residue derived from the production of illuminating gas, giving it the name bicarburet of hydrogen. In 1833, Eilhard Mitscherlich produced it by distilling benzoic lime, he gave the compound the name benzin. In 1836, the French chemist Auguste Laurent named the substance "phène". In 1845, Charles Mansfield, working under August Wilhelm von Hofmann, isolated benzene from coal tar. Four years Mansfield began the first industrial-scale production of benzene, based on the coal-tar method; the sense developed among chemists that a number of substances were chemically related to benzene, comprising a diverse chemical family.
In 1855, Hofmann used the word "aromatic" to designate this family relationship, after a characteristic property of many of its members. In 1997, benzene was detected in deep space; the empirical formula for benzene was long known, but its polyunsaturated structure, with just one hydrogen atom for each carbon atom, was challenging to determine. Archibald Scott Couper in 1858 and Joseph Loschmidt in 1861 suggested possible structures that contained multiple double bonds or multiple rings, but too little evidence was available to help chemists decide on any particular structure. In 1865, the German chemist Friedrich August Kekulé published a paper in French suggesting that the structure contained a ring of six carbon atoms with alternating single and double bonds; the next year he published a much longer paper in German on the same subject. Kekulé used evidence that had accumulated in the intervening years—namely, that there always appeared to be only one isomer of any monoderivative of benzene, that there always appeared to be three isomers of every disubstituted derivative—now understood to correspond to the ortho and para patterns of arene substitution—to argue in support of his proposed structure.
Kekulé's symmetrical ring could explain these curious facts, as well as benzene's 1:1 carbon-hydrogen ratio. The new understanding of benzene, hence of all aromatic compounds, proved to be so important for both pure and applied chemistry that in 1890 the German Chemical Society organized an elaborate appreciation in Kekulé's honor, celebrating the twenty-fifth anniversary of his first benzene paper. Here Kekulé spoke of the creation of the theory, he said that he had discovered the ring shape of the benzene molecule after having a reverie or day-dream of a snake seizing its own tail. This vision, came to him after years of studying the nature of carbon-carbon bonds; this was 7 years after he had solved the problem of how carbon atoms could bond to up to four other atoms at the same time. Curiously, a similar, humorous depiction of benzene had appeared in 1886 in a pamphlet entitled Berichte der Durstigen Chemischen Gesellschaft, a parody of the Berichte der Deutschen Chemischen Gesellschaft, only the parody had monkeys seizing each other in a circle, rather than snakes as in Kekulé's anecdote.
Some historians have suggested that the parody was a lampoon of the snake anecdote already well known through oral transmission if it had not yet appeared in print. Kekulé's 1890 speech in which this anecdote appeared has been translated into English. If the anecdote is the memory of a real event, circumstances mentioned in the story suggest that it must have happened early in 1862; the cyclic nature of benzene was confirmed by the crystallographer Kathleen Lonsdale in 1929. The German chemist Wilhelm Körner suggested the prefixes ortho-, meta-, para- to distinguish di-substituted benzene derivatives in 1867, it was the German chemist Karl Gräbe who, in 1869, first used the prefixes ortho-, meta-, para- to denote specific relative locations of the substituents on a di-substituted aromatic ring (viz, nap
Chemistry is the scientific discipline involved with elements and compounds composed of atoms and ions: their composition, properties and the changes they undergo during a reaction with other substances. In the scope of its subject, chemistry occupies an intermediate position between physics and biology, it is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant chemistry, the formation of igneous rocks, how atmospheric ozone is formed and how environmental pollutants are degraded, the properties of the soil on the moon, how medications work, how to collect DNA evidence at a crime scene. Chemistry addresses topics such as how atoms and molecules interact via chemical bonds to form new chemical compounds. There are four types of chemical bonds: covalent bonds, in which compounds share one or more electron; the word chemistry comes from alchemy, which referred to an earlier set of practices that encompassed elements of chemistry, philosophy, astronomy and medicine.
It is seen as linked to the quest to turn lead or another common starting material into gold, though in ancient times the study encompassed many of the questions of modern chemistry being defined as the study of the composition of waters, growth, disembodying, drawing the spirits from bodies and bonding the spirits within bodies by the early 4th century Greek-Egyptian alchemist Zosimos. An alchemist was called a'chemist' in popular speech, the suffix "-ry" was added to this to describe the art of the chemist as "chemistry"; the modern word alchemy in turn is derived from the Arabic word al-kīmīā. In origin, the term is borrowed from the Greek χημία or χημεία; this may have Egyptian origins since al-kīmīā is derived from the Greek χημία, in turn derived from the word Kemet, the ancient name of Egypt in the Egyptian language. Alternately, al-kīmīā may derive from χημεία, meaning "cast together"; the current model of atomic structure is the quantum mechanical model. Traditional chemistry starts with the study of elementary particles, molecules, metals and other aggregates of matter.
This matter can be studied in isolation or in combination. The interactions and transformations that are studied in chemistry are the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together; such behaviors are studied in a chemistry laboratory. The chemistry laboratory stereotypically uses various forms of laboratory glassware; however glassware is not central to chemistry, a great deal of experimental chemistry is done without it. A chemical reaction is a transformation of some substances into one or more different substances; the basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation, which involves atoms as subjects; the number of atoms on the left and the right in the equation for a chemical transformation is equal. The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.
Energy and entropy considerations are invariably important in all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions, they can be analyzed using the tools of e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists. Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry; the particles that make up matter have rest mass as well – not all particles have rest mass, such as the photon. Matter can be a mixture of substances; the atom is the basic unit of chemistry. It consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud; the nucleus is made up of positively charged protons and uncharged neutrons, while the electron cloud consists of negatively charged electrons which orbit the nucleus. In a neutral atom, the negatively charged electrons balance out the positive charge of the protons.
The nucleus is dense. The atom is the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state, coordination number, preferred types of bonds to form. A chemical element is a pure substance, composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol Z; the mass number is the sum of the number of neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same