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Chemical element

species of atoms having the same number of protons in the atomic nucleus and the same chemical properties, but not necessarily the same mass, or the same stability (or half-lifetime if they are unstable)

A chemical element is a chemical substance that cannot be broken down into other substances by chemical reactions. The basic particle that constitutes a chemical element is the atom. Chemical elements are identified by the number of protons in the nuclei of their atoms, known as the element's atomic number.

    Periodic Table of
Chemical Elements

Quotes

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  • I have presented the periodic table as a kind of travel guide to an imaginary country, of which the elements are the various regions. This kingdom has a geography: the elements lie in particular juxtaposition to one another, and they are used to produce goods, much as a prairie produces wheat and a lake produces fish. It also has a history. Indeed, it has three kinds of history: the elements were discovered much as the lands of the world were discovered; the kingdom was mapped, just as the world was mapped, and the relative positions of the elements came to take on a great significance; and the elements have their own cosmic history, which can be traced back to the stars.
    • Peter Atkins, The Periodic Kingdom: A Journey into the Land of the Chemical Elements (1995) Preface.
  • It was a great achievement of the early chemists—with the crude experimental techniques available also with the ever-astonishing power of human reason... to discover this reduction of the world to its components, the chemical elements. Such reduction does not destroy its charm but adds understanding to sensation, and this understanding only deepens our delight.
    • Peter Atkins, The Periodic Kingdom: A Journey into the Land of the Chemical Elements (1995) pp. 147-148.
  • I have raised a question which may be regarded as heretical. At the time when our modern conception of chemistry first dawned... the average chemist... accepted the elements as ultimate facts... absolutely simple, incapable of transmutation or decomposition, each a kind of barrier behind which we could not penetrate. ...[H]e said they were self-existent from all eternity ...But in our times... we cannot help asking what are the elements, whence do they come, what is their signification? ...These elements perplex us in our researches, baffle us in our speculations, and haunt us in our very dreams. They stretch like an unknown sea before us—mocking, mystifying and murmuring strange revelations and possibilities.
    If I venture to say that... elements are not simple and primordial... but have evolved from simpler matters—or... one sole kind of matter—I... give formal utterance to an idea... for some time "in the air" of science. Chemists, physicists, philosophers of the highest merit declare explicitly their belief that the seventy... elements of our text-books are not the pillars of Hercules which we must never hope to pass.
  • 1. Small particles called atoms exist and compose all matter; 2. They are indivisible and indestructible; 3. Atoms of the same chemical element have the same chemical properties and do not transmute or change into different elements.
  • That the forms of natural bodies may depend upon different arrangements of the same particles of matter has been a favourite hypothesis advanced in the earliest era of physical research, and often supported by the reasonings of the ablest philosophers. This sublime chemical speculation sanctioned by the authority of Hooke, Newton, and Boscovich, must not be confounded with the ideas advanced by the alchemists concerning the convertibility of the elements into each other. The possible transmutation of metals has generally been reasoned upon not as a philosophical research, but as an empirical process. Those who have asserted the actual production of the precious metals from other elements, or their decomposition, or who have defended the chimera of the philosopher's stone, have been either impostors, or men deluded by impostors. In this age of rational inquiry it will be useless to decry the practices of the adepts, or to caution the public against confounding the hypothetical views respecting the elements founded upon distinct analogies, with the dreams of alchemical visionaries, most of whom, as an author of the last century justly observed, professed an art without principles, the beginning of which was deceit, the progress delusion, and the end poverty.
  • [C]hlorine possesses the singular power of removing the hydrogen of certain bodies, replacing it atom for atom. This law of nature, this law or theory of substitutions... I propose to call... metalepsy, from μετάληψις, which expresses... that the body... has taken one element in place of another, chlorine in place of hydrogen, for example. Thus chloral is formed by substitution, or by metalepsy; it is one of the maleptic products of alcohol. ...acetic ether, acetic acid, formic acid are maleptic products of alcohol.
    • Jean-Baptiste Dumas, Recherches de Chimie organique p. 545-549 as quoted by Henry Marshall Leicester, Herbert S. Klickstein, A Source Book in Chemistry, 1400-1900 (1952) "Researches in Organic Chemistry Relative to the Action of Chlorine in Alcohol" p. 322.
  • Some recent work by E. Fermi and L. Szilard, which has been communicated to me in manuscript, leads me to expect that the element uranium may be turned into a new and important source of energy in the immediate future. Certain aspects of the situation seem to call for watchfulness and, if necessary, quick action on the part of the Administration...
  • Although the problem of transmuting chemical elements into each other is much older than a satisfactory definition of the very concept of chemical element, it is well known that the first and most important step towards its solution was made only nineteen years ago by the late Lord Rutherford, who started the method of the nuclear bombardments.
  • [T]he purpose of my paper would be entirely attained if I succeed in turning the attention of investigators to the relationships in the size of the atomic weights of nonsimilar elements, which have, as far as I know, been almost entirely neglected until now.
  • No matter how properties of simple bodies may change in the free state, something remains constant, and when the element forms compounds, this something is material existence and establishes the characteristics of the compounds, which include the given element. In this respect we know only one constant peculiar to an element, namely the atomic weight. The size of the atomic weight, by the very essence of matter, is common to the simple body and all its compounds. Atomic weight belongs not to coal or diamond, but to carbon.
  • 1. The elements, if arranged according to their atomic weights, exhibit an evident periodicity of properties.
    2. Elements which are similar as regards their chemical properties have atomic weights which are either of nearly the same value (e.g., platinum, iridium, osmium) or which increase regularly (e.g., potassium, rubidium, caesium).
    3. The arrangement of the elements, or of groups of elements in the order of their atomic weights corresponds to their so-called valencies as well as, to some extent, to their distinctive chemical properties--as is apparent among other series in that of lithium, beryllium, barium, carbon, nitrogen, oxygen and iron [sic. The printed speech in J. Chem. Soc. says barium and iron. Obviously boron (B) and fluorine (F) are meant. Mendeleev's 1869 paper lists the symbols B and F rather than the names of the elements.--CJG]
    4. The elements which are the most widely diffused have small atomic weights.
    5. The magnitude of the atomic weight determines the character of the element just as the magnitude of the molecule determines the character of a compound body.
    6. We must expect the discovery of many yet unknown elements, for example, elements analogous to aluminium and silicon, whose atomic weight would be between 65 and 75.
    7. The atomic weight of an element may sometimes be amended by a knowledge of those of the contiguous elements. Thus, the atomic weight of tellurium must lie between 123 and 126, and cannot be 128.
    8. Certain characteristic properties of the elements can be foretold from their atomic weights.
    ...[R]elations ...exist between the atomic weights of dissimilar elements ...hitherto ...neglected. I believe that the solution of some of the most important problems of our science lies in researches of this kind. To-day, 20 years after the above conclusions were formulated, they may still be considered as expressing the essence of the now well-known periodic law.
 
Periodic classification of Elements
  • The Bakerian lecture in which Davy announces the discovery of the compound nature of the fixed alkalis opens with a reference to the concluding remarks of his lecture of the previous year, "that the new methods of investigation promised to lead to a more intimate knowledge than had hitherto been obtained concerning the true elements of bodies. This conjecture, then sanctioned only by strong analogies, I am now happy to be able to support by some conclusive facts."
  • It was taught by some chemists that an alkali is hidden in every earth, and by others that an alkali is an earth refined by the presence of acid and combustible matter. Black's exact quantitative investigations tended to disparage all such explanations as these; but it yet remained to find the precise composition the alkalis and the earths. Lavoisier thought that these bodies must be compounds; but, as he had no means of proving this, he classed them with the elements, while suggesting that the earths were probably compounds of oxygen with unknown metals.
 
Sodium visible light spectrum
  • So let us listen to the light—what music do we hear? For one thing, we can elicit from each chemical element its own, unique chord. You may sometimes have noticed that a bright yellow flash is produced if ordinary table salt is sprinkled on a flame...a first bare hint of the subject of flame spectra... The fact that different elements emit light with different color characteristics is exploited by the makers of fireworks.

A Dictionary of Chemistry (1777)

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Containing the Theory and Practice of that Science: Its Application to Natural Philosophy, Natural History, Medicine, and Animal Economy: With Full Explanations of the Qualities and Modes of Action of Chemical Remedies: And the Fundamental Principles of the Arts, Trades and Manufactures, Dependent on Chemistry. Translated from the French, with Notes, Additions, and Plates. The Second Edition. To which is Added, as an Appendix, A Treatise on the Various Kinds of Permanently, Elastic Fluids, or Gases. A translation of Dictionnaire de Chymie (1766) which is attributed to Pierre-Joseph Macquer. See Earths & Earth (historical chemistry)
  • Earth is one of the four simple substances called elements, or primitive principles; because they are indeed the most simple of all those which enter into the combination of compound bodies. We cannot doubt, in particular, that the greatest part of the compounds which we can analyse contain earth as one of their principles; for after art has exhausted all its efforts to decompose them, a fixed and solid matter always remains, upon which no change can be produced; and this is what is generally called earth. It has the solidity, weight, fixity, and other principal properties of the mass of solid matter which forms the globe we inhabit, called also the earth.
  • These general considerations are sufficient to convince us, that in nature a substance exists whose properties are different from those of fire, air, water; and which is, like these other substances, one of the elements of compound bodies. But a vague assertion like this does not satisfy chemists. Besides the ascertaining of the exigence of the different substances submitted to their examination, they require to know the properties of these substances in their greatest degree of purity and simplicity; but they have found much difficulty and uncertainty in investigating the essential properties of the purest and simplest terrestrial element.
  • Earth is not found so pure as the other elements, fire, air, and water, which, though not entirely free from mixture, are however so pure, that we may certainly and easily discover their fundamental properties. These properties of each of these pure elements are so well ascertained, and so evident, that nobody has yet attempted to distinguish different kinds of fire, air, or water, notwithstanding the differences which may arise from the heterogeneous substances with which they are almost always mixed.
  • But we cannot say the same of earth; for a considerable number of substances are called earths, because they possess the principal properties of the terrestrial element: but these substances, when examined more particularly, are always found to differ from each other so much in other respects, and to be so difficultly purifiable from heterogeneous matter, that we have not ascertained whether only one simple and elementary earth, or several ones essentially different, although equally simple, exist.
  • The most general and most probable opinion is, that as only one kind of fire, of air, and of water, so only one kind of simple elementary earth, exists. Alchemists chiefly have endeavoured to discover this primary earth, not with an intention to ascertain its properties, but because they imagined that as gold is the purest of metals, the earth of which it is partly composed must be also the most pure; they have, therefore, searched every where for this earth, which they call pure earth and virgin earth. They have endeavoured to obtain it from dew, rain, the air, ashes of vegetables, animals, and several minerals: but it was impossible to find it in compound bodies; for we shall see that when once this element makes part of a compound body, it cannot be disengaged from the substances with which it has united.
  • As earth is an element... it deserves an accurate investigation to discover which is the most simple and elementary of all the substances to which the name earth has been applied.

The Elements of Chemical Philosophy (1812)

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by Humphry Davy, Introduction, Part I. Vol. I of Historical View of the Progress of Chemistry
  • Van Helmont of Brussels... was formed in the school of Alchemy, and his mind was tinctured with its prejudices: but his views concerning nature and the elements were distinguished by much more philosophical acuteness, and more sagacity, than those of any former writer. He is the first person who seems to have had any idea respecting elastic fluids, different from the air of the atmosphere; and he has distinctly mentioned three of these substances, to which he applied the term gases: namely aqueous gas or steam, unctuous or inflammable gas, and gas from wood or carbonic acid gas. Van Helmont developed some accurate views respecting the permanent elasticity of air, and the operation of heat upon it; and a sketch of a curious instrument very similar to the differential thermometer, is to be found in his works.
    • pp. 18-19.
  • Boyle was one of the most active experimenters, and certainly the greatest chemist of his age. He introduced the use of tests or reagents, active substances for detecting the presence of other bodies: he overturned the [prevalent] ideas... that the results of operations by fire were the real elements of things, and he ascertained... important facts respecting inflammable bodies, acids, alkalies, and the phænomena of combination; but neither he nor any of his contemporaries endeavoured to account for the changes of bodies by any fixed principles.
    • p. 27.
  • Beccher, ...after having studied with minute attention, the operations of metallurgy, and the phænomena of the mineral kingdom, formed the bold idea of explaining the whole system of the earth by the mutual agency and changes of a few elements. And by supposing the existence of a vitrifiable, a metallic, and an inflammable earth, he attempted to account for the various productions of rocks, crystalline bodies, and metallic veins, assuming a continued interchange of principles between the atmosphere, the ocean, and the solid surface of the globe, and considering the operations of nature as all capable of being imitated by art.
    • p. 29
  • Dr. Hales... resumed the investigations commenced with so much success by Boyle, Hooke, and Mayow; and endeavoured to ascertain the chemical relations of air to other substances, and to ascertain by statical experiments the cases in nature, in which it is absorbed or emitted. ...[B]ut, misled by the notion of one elementary principle constituting elastic matter... he formed few inferences connected with the refined philosophy of the subject...
    • p. 33
  • It was felt by many philosophers, particularly by the illustrious Bergman, that an improvement in chemical nomenclature was necessary, and in 1787, Messrs. Lavoisier, Morveau, Berthollet, and Fourcroy, presented to the world a plan for an almost entire change in the denomination of chemical substances, founded upon the idea of calling simple bodies by some names characteristic of their most striking qualities, and of naming compound bodies from the elements which composed them.
    • p. 45.
  • Simplicity and precision ought to be the characteristics of a scientific nomenclature: words should signify things, or the analogies of things, and not opinions. If all the elements were certainly known, the principle adopted by Lavoisier would have possessed an admirable application; but a substance in one age supposed to be simple, in another is proved to be compound; and vice versa. A theoretical nomenclature is liable to continued alterations; oxygenated muriatic acid is as improper a name as dephlogisticated marine acid.
    • p. 46.
  • The attempts made to analyse vegetable substances previous to 1720, merely produced their resolution into the supposed elements of the chemists of those days, namely, salts, Earths, phlegm, and sulphur. Boerhaave and Newmann attempted an examination by fluid menstrua, which was pursued with some success by Rouelle, Macquer and Lewis. Scheele, between 1770 and 1780, pointed out several new vegetable acids.
    • pp. 50-51.
  • When one body combines with another in more than one proportion, the second proportion appears to be some multiple or divisor of the first; and this circumstance, observed and ingeniously illustrated by Mr. Dalton, led him to adopt the atomic hypothesis of chemical changes, which had been ably defended by Mr. Higgins in 1789, namely, that the chemical elements consist of certain indestructible particles which unite one and one, or one and two, or in some definite [integer] numbers.
    • p. 56.

The Elements of Chemistry (1904)

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by M. M. Pattison Muir
  • Whether a homogeneous substance is an element or a compound can be determined only by a series of quantitative experiments: if it has been separated into two or more homogeneous substances, and formed by the union of two or more homogeneous substances, it is a compound; if it has not been separated into unlike portions, nor formed by the union of unlike substances, it is an element.
    • Ch.I
  • Lavoisier's quantitative examination of the change... proved that the total mass of the reacting substances mercury and air, remained unchanged. ...the masses of the two elements which combine are always in the ratio of one of oxygen to 12.5 of mercury. When the compound mercuric oxide is strongly heated, it is changed into the elements mercury and oxygen; the sum of the masses of the two elements obtained is exactly equal to the mass of the compound changed; the masses of the mercuric oxide, mercury, and oxygen, are always in the ratio of 13.5 to 12.5 to 1.
    • Ch.I
  • The composition of a compound is stated in terms of the elements which unite to form it, and can be obtained by its decomposition.
    • Ch.II
  • In... A New System of Chemical Philosophy published in 1808, John Dalton laid the foundations of the atomic theory: he assumed chemical action to be an action between very minute particles of elements and compounds, and all the minute particles of the same element, or compound, to be exactly the same size and weight. ...his hypothesis assumed the accuracy and universal applicability of those generalisations which are now called the laws of chemical combination.
    • Notes to Ch.II

History of Chemistry (1909) vol. 1

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by Sir Thomas Edward Thorpe, Vol. 1 From the Earliest Times to the Middle of the Nineteenth Century
  • All the oldest cosmogonies regarded water as the fundamental principle of things: from Okeanos sprang the gods—themselves deified personifications of the "elements" or principles of which the world was made. ...[T]his doctrine of the origin and essential nature of matter came to be... associated with the name of Thales of Miletus... who, according to Tertullian, is to be regarded as the first of the race of the natural philosophers—that is, the first of those who made it their business to inquire after natural causes and phenomena. Thales... may have been influenced by the Egyptian teaching in the formulation of his cosmological theories.
    • pp. 15-16.
  • Although the idea of a primal "element" or common principle is to be found in every old-world philosophical system, the ancient philosophers were by no means in agreement as to its character. Anaximenes... taught that it was air, Herakleitos of Ephesus that it was fire, and Pherekides that it was earth.
    • pp. 16-17.
  • Empedokles... was the first whose name has come down to us to reintroduce the definite conception of four primal elements—fire, air, water, and earth. These he regarded as distinct, and incapable of being transmuted, but as forming all varieties of matter by intermixture in various proportions. These principles he deified, Zeus being the personification of the element of fire, Here of air, Nestis of water, and Aidoneous of earth.
    • pp. 17-18.
  • The doctrine of the four elements was also adopted by Plato and amplified by Aristotle... [who] exercised an authority almost supreme in Europe during nearly twenty centuries. His influence is to be traced throughout the literature of chemistry long after the time of Boyle. It may be detected even now. ...His theory of the nature of matter is contained in his treatise on Generation and Destruction. It mainly differed from that of Empedokles in regarding the four "elements" as mutually convertible. Each "element" or principle was regarded as being possessed of two qualities, one of which was shared by another element or principle.
    Thus: Fire is hot and dry; air is hot and wet; water is cold and wet; earth is cold and dry.
    In each primal "element" one quality prevails. Fire is more hot than dry; air is more wet than hot; water is more cold than wet; earth is more dry than cold. ...[I]f the dryness of fire is overcome by the moisture of water, air is produced; if the heat of air is overcome by the coldness of earth, water is formed; if the moisture of water is overcome by the dryness of fire, earth results. Ancient chemical literature contains many illustrations or diagrams symbolising the convertibility or mutual relations....
    • p. 18.
  • The supremacy of the old philosophy may be said to have been first distinctly challenged by Robert Boyle. The appearance in 1661 of his book, The Sceptical Chemist, marks a turning-point in the history of chemistry. ...In this treatise Boyle sets out to prove that the number of the peripatetic elements or principles hitherto assumed by chemists is, to say the least, doubtful.
    • pp. 54-55.
  • He concludes... that the Paracelsian elements—their "salt," "sulphur," and "mercury"—are not the first and most simple principles of bodies; but that these consist, at most, of concretions of corpuscles or particles more simple than they, and possessing the radical and universal properties of volume, shape, and motion.
    • p. 55.
  • Boyle was the first to formulate our present conception of an element in contradistinction to that of the Greeks and the schoolmen who influenced the theories of the iatro-chemists. In the sense understood by him, the Aristotelian elements were not true elements, nor were the salt, sulphur, and mercury of the school of Paracelsus.
    • p. 59.
  • He was... the first to define the relation of an element to a compound, and to draw the distinction we still make between compounds and mixtures.
    • p. 59.
  • Prior to the time of Black all forms of gaseous substance were regarded as substantially identical in fact, as being air, as understood by the Ancients a simple elementary substance. It was Black's study of carbonic acid which first clearly established that there were essentially distinct varieties of gaseous matter.
  • p. 69.

History of Chemistry (1910) vol. 2

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by Sir Thomas Edward Thorpe, Vol. 2 From 1850 to 1910
  • Chemists seemed to be of Turner's opinion that the time had arrived for reviewing their stock of information, and for submitting the principal facts and fundamental doctrines to the severest scrutiny. Their activity was employed not so much in searching for new compounds or new elements as in examining those already discovered. The foundations of the atomic theory were being securely laid. The ratios in which the elements of known compounds are united were being more exactly ascertained. The efforts of workers, Graham excepted, seemed to be spent more on points of detail, on the filling-in of little gaps in the chemical structure, as it then existed, than in attempts at new developments.
    • p. 2
  • It was largely through the influence of [the following] master-minds that chemistry took a new departure. Prior to their time organic chemistry hardly existed as a branch of science: organic products, as a rule, were interesting only to the pharmacist mainly by reason of their technical or medicinal importance. But by the middle of the nineteenth century the richness of this hitherto untilled field became manifest, and scores of workers hastened to sow and to reap in it. The most striking feature, indeed, of the history of chemistry during the past sixty years has been the extraordinary expansion of the organic section of the science. The chemical literature relating to the compounds of carbon now exceeds in volume that devoted to all the rest of the elements.
    • p. 11

See also

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