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Avogadro Number
The Avogadro constant, commonly denoted or , is an SI defining constant with an exact value of when expressed in reciprocal moles. It defines the ratio of the number of constituent particles to the amount of substance in a sample, where the particles in question are any designated elementary entity, such as molecules, atoms, ions, ion pairs. The numerical value of this constant is known as the Avogadro number, commonly denoted . The Avogadro ''number'' is an exact number equal to the number of constituent particles in one mole of any substance (by definition of the mole), historically derived from the experimental determination of the number of atoms in 12 grams of carbon-12 (12C) before the 2019 revision of the SI. Both the constant and the number are named after the Italian physicist and chemist Amedeo Avogadro. The Avogadro constant is used as a proportionality factor in relating the ''amount of substance'' , in a sample of a substance , to the corresponding num ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amadeo Avogadro
Lorenzo Romano Amedeo Carlo Avogadro, Count of Quaregna and Cerreto (, also , ; 9 August 17769 July 1856) was an Italian scientist, most noted for his contribution to molecular theory now known as Avogadro's law, which states that equal volumes of gases under the same conditions of temperature and pressure will contain equal numbers of molecules. In tribute to him, the ratio of the number of elementary entities (atoms, molecules, ions or other particles) in a substance to its amount of substance (the latter having the unit mole), , is known as the Avogadro constant. This constant is denoted ''N''A, and is one of the seven defining constants of the SI. Biography Amedeo Avogadro was born in Turin to a noble family of the Kingdom of Sardinia (now part of Italy) in the year 1776. He graduated in ecclesiastical law at the late age of 20 and began to practice. Soon after, he dedicated himself to physics and mathematics (then called ''positive philosophy''), and in 1809 sta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molar Mass
In chemistry, the molar mass () (sometimes called molecular weight or formula weight, but see related quantities for usage) of a chemical substance ( element or compound) is defined as the ratio between the mass () and the amount of substance (, measured in moles) of any sample of the substance: . The molar mass is a bulk, not molecular, property of a substance. The molar mass is a ''weighted'' ''average'' of many instances of the element or compound, which often vary in mass due to the presence of isotopes. Most commonly, the molar mass is computed from the standard atomic weights and is thus a terrestrial average and a function of the relative abundance of the isotopes of the constituent atoms on Earth. The molecular mass (for molecular compounds) and formula mass (for non-molecular compounds, such as ionic salts) are commonly used as synonyms of molar mass, as the numerical values are identical (for all practical purposes), differing only in units ( dalton vs. g/mol o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent). It is vital for all known forms of life, despite not providing food energy or organic micronutrients. Its chemical formula, , indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°. In liquid form, is also called "water" at standard temperature and pressure. Because Earth's environment is relatively close to water's triple point, water exists on Earth as a solid, a liquid, and a gas. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds consist of suspended droplets of water and ice, its solid state. When finely divided, crystalline ice ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accuracy And Precision
Accuracy and precision are two measures of ''observational error''. ''Accuracy'' is how close a given set of measurements (observations or readings) are to their ''true value''. ''Precision'' is how close the measurements are to each other. The International Organization for Standardization (ISO) defines a related measure: ''trueness'', "the closeness of agreement between the arithmetic mean of a large number of test results and the true or accepted reference value." While ''precision'' is a description of ''random errors'' (a measure of statistical variability), ''accuracy'' has two different definitions: # More commonly, a description of ''systematic errors'' (a measure of statistical bias of a given measure of central tendency, such as the mean). In this definition of "accuracy", the concept is independent of "precision", so a particular set of data can be said to be accurate, precise, both, or neither. This concept corresponds to ISO's ''trueness''. # A combination of both ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elementary Entities
In chemistry and physics, a molecular entity, or chemical entity, is "any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion, complex, conformer, etc., identifiable as a separately distinguishable entity". A molecular entity is any singular entity, irrespective of its nature, used to concisely express any type of chemical particle that can exemplify some process: for example, atoms, molecules, ions, etc. can all undergo a chemical reaction. Chemical species is the macroscopic equivalent of molecular entity and refers to sets or ensembles of molecular entities. According to IUPAC, "The degree of precision necessary to describe a molecular entity depends on the context. For example 'hydrogen molecule' is an adequate definition of a certain molecular entity for some purposes, whereas for others it is necessary to distinguish the electronic state and/or vibrational state and/or nuclear spin, etc. of the hydrogen molecule." See also * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dalton (unit)
The dalton or unified atomic mass unit (symbols: Da or u, respectively) is a unit of mass defined as of the mass of an Bound state, unbound neutral atom of carbon-12 in its nuclear and electronic ground state and invariant mass, at rest. It is a Non-SI units mentioned in the SI, non-SI unit accepted for use with SI. The word "unified" emphasizes that the definition was accepted by both IUPAP and IUPAC. The atomic mass constant, denoted , is defined identically. Expressed in terms of , the atomic mass of carbon-12: . Its value in International System of Units, SI units is an experimentally determined quantity. The 2022 CODATA recommended value of the atomic mass constant expressed in the SI base unit kilogram is:This value serves as a Conversion of units, conversion factor of mass from daltons to kilograms, which can easily be converted to Gram, grams and other metric units of mass. The 2019 revision of the SI redefined the kilogram by fixing the value of the Planck constant (), i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Mass
Atomic mass ( or ) is the mass of a single atom. The atomic mass mostly comes from the combined mass of the protons and neutrons in the nucleus, with minor contributions from the electrons and nuclear binding energy. The atomic mass of atoms, ions, or atomic nuclei is slightly less than the sum of the masses of their constituent protons, neutrons, and electrons, due to mass defect (explained by mass-energy equivalence: ). Atomic mass is often measured in dalton (Da) or unified atomic mass unit (u). One dalton is equal to the mass of a carbon-12 atom in its natural state, given by the atomic mass constant , where is the atomic mass of carbon-12. Thus, the numerical value of the atomic mass of a nuclide when expressed in daltons is close to its mass number. The relative isotopic mass (see section below) can be obtained by dividing the atomic mass of an isotope by the atomic mass constant , yielding a dimensionless value. Thus, the atomic mass of a carbon-12 atom is b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gram
The gram (originally gramme; SI unit symbol g) is a Physical unit, unit of mass in the International System of Units (SI) equal to one thousandth of a kilogram. Originally defined in 1795 as "the absolute Mass versus weight, weight of a volume of pure water equal to Cube (algebra), the cube of the hundredth part of a metre [1 Cubic centimetre, cm3], and at Melting point of water, the temperature of Melting point, melting ice", the defining temperature (0 °C) was later changed to the temperature of maximum density of water (approximately 4 °C). Subsequent redefinitions agree with this original definition to within 30 Parts-per notation, parts per million (0.003%), with the maximum density of water remaining very close to 1 g/cm3, as shown by modern measurements. By the late 19th century, there was an effort to make the Base unit (measurement), base unit the kilogram and the gram a derived unit. In 1960, the new International System of Units defined a '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mole Carbon-12 Diagram
Mole (or Molé) may refer to: Animals * Mole (animal) or "true mole" * Golden mole, southern African mammals * Marsupial mole, Australian mammals Other common meanings * Nevus, a growth on human skin ** Melanocytic nevus, a specific type of mole * Mole (architecture), a structure separating bodies of water * Mole (espionage), a spy in an organisation * Mole (sauce), a traditional Mexican food which can be a sauce or marinade * An abnormal mass within the uterus; see molar pregnancy Arts and entertainment * Mole, in the novel ''The Wind in the Willows'' by Kenneth Grahame * Mole (Zdeněk Miler character) * The Mole, in '' Happy Tree Friends'' * The Mole, a criminal in Dick Tracy comic strips * '' El Topo'' (''The Mole''), a 1970 film * ''De Mol'' (TV series) * "The Mole", a song by Harry James Science and technology * Mole (unit), the SI unit for the amount of substance * Tunnel boring machine * Heat Flow and Physical Properties Package, a burrowing probe sent to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal Structure
In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in a material that constitutes this repeating pattern is the unit cell of the structure. The unit cell completely reflects the symmetry and structure of the entire crystal, which is built up by repetitive translation of the unit cell along its principal axes. The translation vectors define the nodes of the Bravais lattice. The lengths of principal axes/edges, of the unit cell and angles between them are lattice constants, also called ''lattice parameters'' or ''cell parameters''. The symmetry properties of a crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. The word ''crystal'' derives from the Ancient Greek word (), meaning both "ice" and " rock crystal", from (), "icy cold, frost". Examples of large crystals include snowflakes, diamonds, and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Polycrystals include most metals, rocks, ceramics, and ice. A third cat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanometre
330px, Different lengths as in respect to the Molecule">molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling), is a unit of length in the International System of Units (SI), equal to one billionth ( short scale) or one thousand million (long scale) of a meter (0.000000001 m) and to 1000 picometres. One nanometre can be expressed in scientific notation as 1 × 10−9 m and as m. History The nanometre was formerly known as the "''millimicrometre''" – or, more commonly, the "''millimicron''" for short – since it is of a micrometer. It was often denoted by the symbol ''mμ'' or, more rarely, as ''μμ'' (however, ''μμ'' should refer to a ''millionth'' of a micron). Etymology The name combines the SI prefix '' nano-'' (from the Ancient Greek , ', "dwarf") with the parent unit name ''metre'' (from Greek , ', "unit of measurement"). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
