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  2. Pivot element - Wikipedia

    en.wikipedia.org/wiki/Pivot_element

    The pivot or pivot element is the element of a matrix, or an array, which is selected first by an algorithm (e.g. Gaussian elimination, simplex algorithm, etc.), to do certain calculations. In the case of matrix algorithms, a pivot entry is usually required to be at least distinct from zero, and often distant from it; in this case finding this ...

  3. Scale (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Scale_(chemistry)

    The scale of a chemical process refers to the rough ranges in mass or volume of a chemical reaction or process that define the appropriate category of chemical apparatus and equipment required to accomplish it, and the concepts, priorities, and economies that operate at each. While the specific terms used—and limits of mass or volume that ...

  4. Size consistency and size extensivity - Wikipedia

    en.wikipedia.org/wiki/Size_consistency_and_size...

    In quantum chemistry, size consistency and size extensivity are concepts relating to how the behaviour of quantum-chemistry calculations changes with the system size. Size consistency (or strict separability) is a property that guarantees the consistency of the energy behaviour when interaction between the involved molecular subsystems is nullified (for example, by distance).

  5. Hardnesses of the elements (data page) - Wikipedia

    en.wikipedia.org/wiki/Hardnesses_of_the_elements...

    Hardnesses of the elements (data page) ... Brinell scale This page was last edited on 16 November 2024, at 12:16 (UTC). Text is available under the ...

  6. Glossary of chemistry terms - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_chemistry_terms

    Also acid ionization constant or acidity constant. A quantitative measure of the strength of an acid in solution expressed as an equilibrium constant for a chemical dissociation reaction in the context of acid-base reactions. It is often given as its base-10 cologarithm, p K a. acid–base extraction A chemical reaction in which chemical species are separated from other acids and bases. acid ...

  7. Space-filling model - Wikipedia

    en.wikipedia.org/wiki/Space-filling_model

    In chemistry, a space-filling model, also known as a calotte model, is a type of three-dimensional (3D) molecular model where the atoms are represented by spheres whose radii are proportional to the radii of the atoms and whose center-to-center distances are proportional to the distances between the atomic nuclei, all in the same scale. Atoms ...

  8. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    Each chemical element has a unique atomic number (Z— for "Zahl", German for "number") representing the number of protons in its nucleus. [4] Each distinct atomic number therefore corresponds to a class of atom: these classes are called the chemical elements. [5] The chemical elements are what the periodic table classifies and organizes.

  9. Reactivity series - Wikipedia

    en.wikipedia.org/wiki/Reactivity_series

    In chemistry, a reactivity series (or reactivity series of elements) is an empirical, calculated, and structurally analytical progression [1] ...