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Chemical Formula
A CHEMICAL FORMULA is a way of expressing information about the proportions of atoms that constitute a particular chemical compound , using a single line of chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and _plus_ (+) and _minus_ (−) signs. These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a chemical name , and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula . Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances , and are generally more limited in power than are chemical names and structural formulas. The simplest types of chemical formulas are called _empirical formulas _, which use letters and numbers indicating the numerical _proportions_ of atoms of each type. _Molecular formulas_ indicate the simple _numbers_ of each type of atom in a molecule, with no information on structure. For example, the empirical formula for glucose is CH2O (twice as many hydrogen atoms as carbon and oxygen), while its molecular formula is C6H12O6 (12 hydrogen atoms, six carbon and oxygen atoms)
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Structural Formula
The STRUCTURAL FORMULA of a chemical compound is a graphic representation of the molecular structure, showing how the atoms are arranged. The chemical bonding within the molecule is also shown, either explicitly or implicitly. Unlike CHEMICAL formulas , which have a limited number of symbols and are capable of only limited descriptive power, STRUCTURAL formulas provide a complete geometric representation of the molecular structure. For example, many chemical compounds exist in different isomeric forms, which have different enantiomeric structures but the same chemical formula . A structural formula is able to indicate arrangements of atoms in three dimensional space in a way that a chemical formula may not be able to do. Several systematic chemical NAMING formats, as in chemical databases , are used that are equivalent to, and as powerful as, geometric structures. These chemical nomenclature systems include SMILES , InChI and CML . These systematic chemical names can be converted to structural formulas and vice versa, but chemists nearly always describe a chemical reaction or synthesis using structural formulas rather than chemical names, because the structural formulas allow the chemist to visualize the molecules and the structural changes that occur in them during chemical reactions
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Aluminium Sulfate
ALUMINIUM SULFATE is a chemical compound with the formula Al 2(SO4) 3. It is soluble in water and is mainly used as a coagulating agent (promoting particle collision by neutralizing charge) in the purification of drinking water and waste water treatment plants, and also in paper manufacturing. Aluminium sulfate is sometimes referred to as a type of alum . Alums are double sulfate salts, with the formula _AM_(SO 4) 2·12H 2O, where A is a monovalent cation such as potassium or ammonium and M is a trivalent metal ion such as aluminium . The anhydrous form occurs naturally as a rare mineral millosevichite , found e.g. in volcanic environments and on burning coal-mining waste dumps. Aluminium sulfate is rarely, if ever, encountered as the anhydrous salt. It forms a number of different hydrates , of which the hexadecahydrate Al2(SO4)3•16H2O and octadecahydrate Al2(SO4)3•18H2O are the most common. The heptadecahydrate, whose formula can be written as 2(SO4)3•5H2O, occurs naturally as the mineral alunogen
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Water
WATER is a transparent and nearly colorless chemical substance that is the main constituent of Earth's streams , lakes , and oceans , and the fluids of most living organisms . Its chemical formula is H2O, meaning that its molecule contains one oxygen and two hydrogen atoms , that are connected by covalent bonds . Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure ; but it often refers also to its solid state (ice ) or its gaseous state (steam or water vapor ). It also occurs in nature as snow , glaciers , ice packs and icebergs , clouds , fog , dew , aquifers , and atmospheric humidity . Water covers 71% of the Earth's surface. It is vital for all known forms of life . On Earth, 96.5% of the planet's crust water is found in seas and oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air as vapor , clouds (formed of ice and liquid water suspended in air), and precipitation . Only 2.5% of this water is freshwater , and 98.8% of that water is in ice (excepting ice in clouds) and groundwater . Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products. A greater quantity of water is found in the earth's interior
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Butane
BUTANE (/ˈbjuːteɪn/ ) is an organic compound with the formula C4H10 that is an alkane with four carbon atoms . Butane is a gas at room temperature and atmospheric pressure. The term may refer to either of two structural isomers , _N_-BUTANE or ISOBUTANE (also called "methylpropane"), or to a mixture of these isomers . In the IUPAC nomenclature, however, "butane" refers only to the _n_-butane isomer (which is the isomer with the unbranched structure). Butanes are highly flammable, colorless, easily liquefied gases . The name butane comes from the roots but- (from butyric acid , named after the Greek word for butter) and -ane . It was discovered by the chemist Edward Frankland in 1849. CONTENTS * 1 Isomers * 2 Reactions * 3 Uses * 4 Effects and health issues * 5 See also * 6 References * 7 External links ISOMERS Common name NORMAL BUTANE UNBRANCHED BUTANE _N_-BUTANE ISOBUTANE _I_-BUTANE IUPAC name BUTANE 2-METHYLPROPANE Molecular diagram Skeletal diagram Rotation about the central C−C bond produces two different conformations (_trans_ and _gauche_) for _n_-butane. REACTIONS Spectrum of the blue flame from a butane torch showing CH molecular radical band emission and C2 Swan bands When oxygen is plentiful, butane burns to form carbon dioxide and water vapor; when oxygen is limited, carbon (soot ) or carbon monoxide may also be formed
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Atom
Atom, from the Greek word atomos, which means indivisible, was first conceived around 2,400 years ago by a Greek man named Democritus . An ATOM is the smallest constituent unit of ordinary matter that has the properties of a chemical element . Every solid , liquid , gas , and plasma is composed of neutral or ionized atoms. Atoms are very small; typical sizes are around 100 picometers (a ten-billionth of a meter, in the short scale ). Atoms are small enough that attempting to predict their behavior using classical physics – as if they were billiard balls, for example – gives noticeably incorrect predictions due to quantum effects . Through the development of physics, atomic models have incorporated quantum principles to better explain and predict the behavior. Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and typically a similar number of neutrons . Protons and neutrons are called nucleons . More than 99.94% of an atom's mass is in the nucleus. The protons have a positive electric charge , the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, that atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion
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Chemical Compound
A CHEMICAL COMPOUND (or just COMPOUND if used in the context of chemistry ) is an entity consisting of two or more atoms , at least two from different chemical elements , which associate via chemical bonds . There are four types of compounds, depending on how the constituent atoms are held together: molecules held together by covalent bonds , ionic compounds held together by ionic bonds , intermetallic compounds held together by metallic bonds , and certain complexes held together by coordinate covalent bonds . Many chemical compounds have a unique numerical identifier assigned by the Chemical Abstracts Service (CAS): its CAS number . A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using the standard abbreviations for the chemical elements, and subscripts to indicate the number of atoms involved. For example, water is composed of two hydrogen atoms bonded to one oxygen atom: the chemical formula is H2O. A compound can be converted to a different chemical composition by interaction with a second chemical compound via a chemical reaction . In this process, bonds between atoms are broken in both of the interacting compounds, and then bonds are reformed so that new associations are made between atoms
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Chemical Element
A CHEMICAL ELEMENT or ELEMENT is a species of atoms having the same number of protons in their atomic nuclei (i.e. the same atomic number , or _Z_). There are 118 elements that have been identified, of which the first 94 occur naturally on Earth
Earth
with the remaining 24 being synthetic elements . There are 80 elements that have at least one stable isotope and 38 that have exclusively radioactive isotopes , which decay over time into other elements. Iron
Iron
is the most abundant element (by mass ) making up Earth, while oxygen is the most common element in the Earth\'s crust . Chemical elements constitute all of the ordinary matter of the universe. However astronomical observations suggest that ordinary observable matter makes up only about 15% of the matter in the universe: the remainder is dark matter ; the composition of this is unknown, but it is not composed of chemical elements. The two lightest elements, hydrogen and helium , were mostly formed in the Big Bang and are the most common elements in the universe. The next three elements (lithium , beryllium and boron ) were formed mostly by cosmic ray spallation , and are thus rarer than heavier elements. Formation of elements with from 6 to 26 protons occurred and continues to occur in main sequence stars via stellar nucleosynthesis . The high abundance of oxygen, silicon , and iron on Earth
Earth
reflects their common production in such stars
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Chemical Nomenclature
A CHEMICAL NOMENCLATURE is a set of rules to generate systematic names for chemical compounds . The nomenclature used most frequently worldwide is the one created and developed by the International Union of Pure and Applied Chemistry (IUPAC). The IUPAC's rules for naming organic and inorganic compounds are contained in two publications, known as the _Blue Book _ and the _Red Book _, respectively. A third publication, known as the _Green Book _, describes the recommendations for the use of symbols for physical quantities (in association with the IUPAP ), while a fourth, the _Gold Book _, contains the definitions of a large number of technical terms used in chemistry. Similar compendia exist for biochemistry (the _White Book_, in association with the IUBMB ), analytical chemistry (the _Orange Book _), macromolecular chemistry (the _Purple Book_) and clinical chemistry (the _Silver Book_)
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Molecule
A MOLECULE is an electrically neutral group of two or more atoms held together by chemical bonds . Molecules are distinguished from ions by their lack of electrical charge . However, in quantum physics , organic chemistry , and biochemistry , the term _molecule_ is often used less strictly, also being applied to polyatomic ions . In the kinetic theory of gases , the term _molecule_ is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are in fact monoatomic molecules. A molecule may be homonuclear , that is, it consists of atoms of one chemical element , as with oxygen (O2); or it may be heteronuclear , a chemical compound composed of more than one element, as with water (H2O). Atoms and complexes connected by non-covalent interactions , such as hydrogen bonds or ionic bonds , are generally not considered single molecules. Molecules as components of matter are common in organic substances (and therefore biochemistry). They also make up most of the oceans and atmosphere. However, the majority of familiar solid substances on Earth, including most of the minerals that make up the crust , mantle , and core of the Earth , contain many chemical bonds, but are _not_ made of identifiable molecules
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Chemical Substance
A CHEMICAL SUBSTANCE also known as a PURE SUBSTANCE is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be chemical elements , chemical compounds , ions or alloys . Chemical substances are often called 'pure' to set them apart from mixtures . A common example of a chemical substance is pure water ; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory . Other chemical substances commonly encountered in pure form are diamond (carbon), gold , table salt (sodium chloride ) and refined sugar (sucrose ). However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical. Chemical substances exist as solids , liquids , gases , or plasma , and may change between these phases of matter with changes in temperature or pressure . Chemical substances may be combined or converted to others by means of chemical reactions . Forms of energy , such as light and heat , are not matter, and are thus not "substances" in this regard
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Empirical Formula
In chemistry , the EMPIRICAL FORMULA of a chemical compound is the simplest positive integer ratio of atoms present in a compound. A simple example of this concept is that the empirical formula of sulfur monoxide , or SO, would simply be SO, as is the empirical formula of disulfur dioxide , S2O2. This means that sulfur monoxide and disulfur dioxide , both compounds of sulfur and oxygen , will have the same empirical formula. However, their chemical formulas , which express the number of atoms in each molecule of a chemical compound, will not be the same. An empirical formula makes no mention of the arrangement or number of atoms. It is standard for many ionic compounds , like calcium chloride (CaCl2), and for macromolecules , such as silicon dioxide (SiO2). The molecular formula , on the other hand, shows the number of each type of atom in a molecule. The structural formula shows the arrangement of the molecule. It is also possible for different types of compounds to have equal empirical formulas. Samples are analyzed in specific elemental analysis tests to determine what percent of a particular element the sample is composed of. EXAMPLES * Glucose
Glucose
(C6H12O6), ribose (C5H10O5), acetic acid (C2H4O2), and formaldehyde (CH2O) all have different molecular formulas but the same empirical formula: CH2O
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Condensed Formula
The STRUCTURAL FORMULA of a chemical compound is a graphic representation of the molecular structure, showing how the atoms are arranged. The chemical bonding within the molecule is also shown, either explicitly or implicitly. Unlike CHEMICAL formulas , which have a limited number of symbols and are capable of only limited descriptive power, STRUCTURAL formulas provide a complete geometric representation of the molecular structure. For example, many chemical compounds exist in different isomeric forms, which have different enantiomeric structures but the same chemical formula . A structural formula is able to indicate arrangements of atoms in three dimensional space in a way that a chemical formula may not be able to do. Several systematic chemical NAMING formats, as in chemical databases , are used that are equivalent to, and as powerful as, geometric structures. These chemical nomenclature systems include SMILES , InChI and CML . These systematic chemical names can be converted to structural formulas and vice versa, but chemists nearly always describe a chemical reaction or synthesis using structural formulas rather than chemical names, because the structural formulas allow the chemist to visualize the molecules and the structural changes that occur in them during chemical reactions
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Chemical Bond
A CHEMICAL BOND is a lasting attraction between atoms that enables the formation of chemical compounds . The bond may result from the electrostatic force of attraction between atoms with opposite charges, or through the sharing of electrons as in the covalent bonds . The strength of chemical bonds varies considerably; there are "strong bonds" or "primary bond" such as metallic , covalent or ionic bonds and "weak bonds" or "secondary bond" such as Dipole-dipole interaction , the London dispersion force and hydrogen bonding . Since opposite charges attract via a simple electromagnetic force , the negatively charged electrons that are orbiting the nucleus and the positively charged protons in the nucleus attract each other. An electron positioned between two nuclei will be attracted to both of them, and the nuclei will be attracted toward electrons in this position. This attraction constitutes the chemical bond. Due to the matter wave nature of electrons and their smaller mass, they must occupy a much larger amount of volume compared with the nuclei, and this volume occupied by the electrons keeps the atomic nuclei in a bond relatively far apart, as compared with the size of the nuclei themselves. In general, strong chemical bonding is associated with the sharing or transfer of electrons between the participating atoms
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