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Atomic number

Neutral atoms of an element contain an equal number of protons and electrons. The number of protons determines an element’s atomic number (Z) and distinguishes one element from another. For example, carbon’s atomic number (Z) is 6 because it has 6 protons. The number of neutrons can vary to produce isotopes, which are atoms of the same […]

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Chelation is a process in which a polydentate ligand bonds to a metal ion, forming a ring. The complex produced by this process is called a chelate, and the polydentate ligand is referred to as a chelating agent. The term chelate was first applied in 1920 by Sir Gilbert T. Morgan and H.D.K. Drew, who

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Mass number

An element’s mass number (A) is the sum of the number of protons and the number of neutrons. The small contribution of mass from electrons is disregarded in calculating the mass number. This approximation of mass can be used to easily calculate how many neutrons an element has by simply subtracting the number of protons from the

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Stable nuclide

Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes. Only 90 nuclides of the first 40 elements are energetically stable for any type of decay except, in theory, proton

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Freezing (or solidification) is a phase transition where a liquid (a disordered structure) turns into a solid (a more ordered structure) when its temperature is lowered below its freezing point. The IUPAC officially adopts the term “solidification” also to refer to the transition of state between the gas phase and the solid phase (which is commonly

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Galvanization is an industrial chemical process of protection against corrosion (galvanic corrosion), in which a coating of zinc is applied to a metal item, hindering the formation of lettrolytic micro-cells with anodic action in the grain edges. Galvanization guarantees a long duration against atmospheric agents, without the need of periodical maintenance. The galvanized product at the

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Lyoluminescence refers to the emission of light while dissolving a solid into a liquid solvent. It is a form of chemiluminescence. The most common lyoluminescent effect is seen when solid samples which have been heavily irradiated by ionizing radiation are dissolved in water. The total amount of light emitted by the material increases proportionally with the total radiation dose received by the

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Chemiluminescence, is the emission of electromagnetic radiation, particularly in the visible and near infrared, that can accompany a chemical reaction. Particular type of luminescence that accompanies some chemical reactions, such as the slow oxidation of phosphorus and many organic substances in decomposition. When the phenomenon occurs in living organisms, it is more properly called bioluminescence.

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Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state; this transformation occurs with heat acquisition and is, therefore, an endothermic process. Usually, in normal environmental conditions, to pass from solid to gaseous state it is necessary to go through the liquid state. Under certain pressure conditions, as the

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A fluorophore, in analogy to a chromophore, is a component of a molecule which causes a molecule to be fluorescent. It is a functional group in a molecule which will absorb energy of a specific wavelength and re-emit energy at a different (but equally specific) wavelength. The amount and wavelength of the emitted energy depend on

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Weak interaction

The weak interaction, which is also often called the weak force or weak nuclear force, is responsible for some nuclear phenomena such as beta decay of the atomic nuclei associated with radioactivity and acts between leptons and quarks (semileptonic interactions), between only leptons (leptonic interactions) and between only quarks (non-leptonic interactions) through the exchange of massive vector bosons called

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Electrochemiluminescence or electrogenerated chemiluminescence (ECL) is a kind of luminescence produced during electrochemical reactions in solutions. In electrochemiluminescence, electrochemically generated intermediates undergo a high degree of exergonic reaction to produce an electronically excited state and then emits light when relaxed to a lower energy level. This wavelength of emitted photons corresponds to the energy gap between these two states. ECL

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In organic chemistry, the term anhydride (from the Greek άνυδρος, ánhydros, without water) denotes an organic compound containing the functional group -CO-O-CO- In the traditional nomenclature of inorganic chemistry, the term anhydride indicates a compound of oxygen with a non-metallic element which, when combined with water, forms oxygenated acids (oxyacids): thus, for example, sulfuric anhydride SO3 and nitric

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Molecule-based magnets

Molecule-based magnets are materials with magnetic properties similar to those of common ferromagnets (e.g. iron, cobalt, nickel), but in which these properties originate from the electronic characteristics of the molecules that compose it. The difference from traditional magnets is that in the latter, the magnetic behavior is based on a collective property of atoms, with non-zero

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London dispersion force

London dispersion forces (LDF, also known as dispersion forces, London forces, instantaneous dipole–induced dipole forces, Fluctuating Induced Dipole Bonds or loosely as van der Waals forces) identify all those forces that occur at the atomic and molecular level due to instantaneous multipoles as a result of quantum effects. These forces are part of the broader category of van der Waals forces.

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Melting [fusion]

Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid when subjected to an increase in heat given or pressure. The inverse process is solidification/freezing. The conditions under which melting occurs correspond to the so-called melting point, which is characterized by a certain temperature

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Corrosion indicates a natural and irreversible process of slow and continuous consumption of a material, which has as its consequences the deterioration of the characteristics or physical properties of the material initially involved. Corrosion is a phenomenon of electrochemical nature that determines a chemical-physical interaction of the metallic material with the environment that surrounds it. Many

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Carbon [symbol C] (from Latin: carbo “coal”) is a nonmetallic and tetravalent (rarely bivalent) chemical element—making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Individual carbon atoms have an incomplete outermost electron shell. With an atomic number of 6 (six electrons and six protons), the first two electrons

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Electric charge

The electric charge is a type of physical property of matter, scalar and signed, responsible for one of the fundamental interactions of matter, the electromagnetic interaction, and the source of the electromagnetic field. There are two types of electric charges: positive and negative (commonly carried by protons and electrons respectively). Like charges repel each other and unlike

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Boiling point

The boiling point is defined as a thermodynamic state, associated to a determined temperature, called “boiling temperature”, and pressure, in correspondence of which the boiling process takes place. In particular, the boiling temperature is the temperature at which the vapor pressure of a liquid equals the external pressure and the liquid begins to boil: it

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In solid solutions, a superlattice is a crystal structure in which the component species are arranged in a regular and ordered manner. Formation of superlattice is possible if the elements comprising the solid solution have simple, integer ratios. Superlattices were discovered early in 1925 by Johansson and Linde[1] after the studies on gold-copper and palladium-copper systems through their

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With the term polarization is defined – in general – the process as a result of which a concentration of “effects” is manifested towards particular points (called poles) of a system. It can assume different meanings and definitions depending on the field (scientific or humanistic). In electrochemistry, polarization is a dissipative phenomenon that involves the decrease of

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