How are atoms of the same similar elements different from one another what do you call these atoms Brainly?

chemical element, also called element, any substance that cannot be decomposed into simpler substances by ordinary chemical processes. Elements are the fundamental materials of which all matter is composed.

This article considers the origin of the elements and their abundances throughout the universe. The geochemical distribution of these elementary substances in the Earth’s crust and interior is treated in some detail, as is their occurrence in the hydrosphere and atmosphere. The article also discusses the periodic law and the tabular arrangement of the elements based on it. For detailed information about the compounds of the elements, see chemical compound.

At present there are 118 known chemical elements. About 20 percent of them do not exist in nature (or are present only in trace amounts) and are known only because they have been synthetically prepared in the laboratory. Of the known elements, 11 (hydrogen, nitrogen, oxygen, fluorine, chlorine, and the six noble gases) are gases under ordinary conditions, two (bromine and mercury) are liquids (two more, cesium and gallium, melt at about or just above room temperature), and the rest are solids. Elements can combine with one another to form a wide variety of more complex substances called compounds. The number of possible compounds is almost infinite; perhaps a million are known, and more are being discovered every day. When two or more elements combine to form a compound, they lose their separate identities, and the product has characteristics quite different from those of the constituent elements. The gaseous elements hydrogen and oxygen, for example, with quite different properties, can combine to form the compound water, which has altogether different properties from either oxygen or hydrogen. Water clearly is not an element because it consists of, and actually can be decomposed chemically into, the two substances hydrogen and oxygen; these two substances, however, are elements because they cannot be decomposed into simpler substances by any known chemical process. Most samples of naturally occurring matter are physical mixtures of compounds. Seawater, for example, is a mixture of water and a large number of other compounds, the most common of which is sodium chloride, or table salt. Mixtures differ from compounds in that they can be separated into their component parts by physical processes; for example, the simple process of evaporation separates water from the other compounds in seawater.

The modern concept of an element is unambiguous, depending as it does on the use of chemical and physical processes as a means of discriminating elements from compounds and mixtures. The existence of fundamental substances from which all matter is made, however, has been the basis of much theoretical speculation since the dawn of history. The ancient Greek philosophers Thales, Anaximenes, and Heracleitus each suggested that all matter is composed of one essential principle—or element. Thales believed this element to be water; Anaximenes suggested air; and Heracleitus, fire. Another Greek philosopher, Empedocles, expressed a different belief—that all substances are composed of four elements: air, earth, fire, and water. Aristotle agreed and emphasized that these four elements are bearers of fundamental properties, dryness and heat being associated with fire, heat and moisture with air, moisture and cold with water, and cold and dryness with earth. In the thinking of these philosophers all other substances were supposed to be combinations of the four elements, and the properties of substances were thought to reflect their elemental compositions. Thus, Greek thought encompassed the idea that all matter could be understood in terms of elemental qualities; in this sense, the elements themselves were thought of as nonmaterial. The Greek concept of an element, which was accepted for nearly 2,000 years, contained only one aspect of the modern definition—namely, that elements have characteristic properties.

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In the latter part of the Middle Ages, as alchemists became more sophisticated in their knowledge of chemical processes, the Greek concepts of the composition of matter became less satisfactory. Additional elemental qualities were introduced to accommodate newly discovered chemical transformations. Thus, sulfur came to represent the quality of combustibility, mercury that of volatility or fluidity, and salt that of fixity in fire (or incombustibility). These three alchemical elements, or principles, also represented abstractions of properties reflecting the nature of matter, not physical substances.

The important difference between a mixture and a chemical compound eventually was understood, and in 1661 the English chemist Robert Boyle recognized the fundamental nature of a chemical element. He argued that the four Greek elements could not be the real chemical elements because they cannot combine to form other substances nor can they be extracted from other substances. Boyle stressed the physical nature of elements and related them to the compounds they formed in the modern operational way.

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In 1789 the French chemist Antoine-Laurent Lavoisier published what might be considered the first list of elemental substances based on Boyle’s definition. Lavoisier’s list of elements was established on the basis of a careful, quantitative study of decomposition and recombination reactions. Because he could not devise experiments to decompose certain substances, or to form them from known elements, Lavoisier included in his list of elements such substances as lime, alumina, and silica, which now are known to be very stable compounds. That Lavoisier still retained a measure of influence from the ancient Greek concept of the elements is indicated by his inclusion of light and heat (caloric) among the elements.

Seven substances recognized today as elements—gold, silver, copper, iron, lead, tin, and mercury—were known to the ancients because they occur in nature in relatively pure form. They are mentioned in the Bible and in an early Hindu medical treatise, the Caraka-samhita. Sixteen other elements were discovered in the second half of the 18th century, when methods of separating elements from their compounds became better understood. Eighty-two more followed after the introduction of quantitative analytical methods.

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isotope, one of two or more species of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behaviour but with different atomic masses and physical properties. Every chemical element has one or more isotopes.

An atom is first identified and labeled according to the number of protons in its nucleus. This atomic number is ordinarily given the symbol Z. The great importance of the atomic number derives from the observation that all atoms with the same atomic number have nearly, if not precisely, identical chemical properties. A large collection of atoms with the same atomic number constitutes a sample of an element. A bar of pure uranium, for instance, would consist entirely of atoms with atomic number 92. The periodic table of the elements assigns one place to every atomic number, and each of these places is labeled with the common name of the element, as, for example, calcium, radon, or uranium.

Not all the atoms of an element need have the same number of neutrons in their nuclei. In fact, it is precisely the variation in the number of neutrons in the nuclei of atoms that gives rise to isotopes. Hydrogen is a case in point. It has the atomic number 1. Three nuclei with one proton are known that contain 0, 1, and 2 neutrons, respectively. The three share the place in the periodic table assigned to atomic number 1 and hence are called isotopes (from the Greek isos, meaning “same,” and topos, signifying “place”) of hydrogen.

Many important properties of an isotope depend on its mass. The total number of neutrons and protons (symbol A), or mass number, of the nucleus gives approximately the mass measured on the so-called atomic-mass-unit (amu) scale. The numerical difference between the actual measured mass of an isotope and A is called either the mass excess or the mass defect (symbol Δ; see table).

The specification of Z, A, and the chemical symbol (a one- or two-letter abbreviation of the element’s name, say Sy) in the form AZSy identifies an isotope adequately for most purposes. Thus, in the standard notation, 11H refers to the simplest isotope of hydrogen and 23592U to an isotope of uranium widely used for nuclear power generation and nuclear weapons fabrication. (Authors who do not wish to use symbols sometimes write out the element name and mass number—hydrogen-1 and uranium-235 in the examples above.)

The term nuclide is used to describe particular isotopes, notably in cases where the nuclear rather than the chemical properties of an atom are to be emphasized. The lexicon of isotopes includes three other frequently used terms: isotones for isotopes of different elements with the same number of neutrons, isobars for isotopes of different elements with the same mass number, and isomers for isotopes identical in all respects except for the total energy content of the nuclei.

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