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  2. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    Periodic table of the chemical elements showing the most or more commonly named sets of elements (in periodic tables), and a traditional dividing line between metals and nonmetals. The f-block actually fits between groups 2 and 3; it is usually shown at the foot of the table to save horizontal space.

  3. Permutation - Wikipedia

    en.wikipedia.org/wiki/Permutation

    An arrangement of distinct objects in a circular manner is called a circular permutation. [39] [e] These can be formally defined as equivalence classes of ordinary permutations of these objects, for the equivalence relation generated by moving the final element of the linear arrangement to its front.

  4. Types of periodic tables - Wikipedia

    en.wikipedia.org/wiki/Types_of_periodic_tables

    Theodor Benfey's arrangement is an example of a continuous (spiral) table. First published in 1964, it explicitly showed the location of lanthanides and actinides. The elements form a two-dimensional spiral, starting from hydrogen, and folding their way around two peninsulas, the transition metals, and lanthanides and actinides.

  5. 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 ...

  6. Period (periodic table) - Wikipedia

    en.wikipedia.org/wiki/Period_(periodic_table)

    There are currently seven complete periods in the periodic table, comprising the 118 known elements. Any new elements will be placed into an eighth period; see extended periodic table. The elements are colour-coded below by their block: red for the s-block, yellow for the p-block, blue for the d-block, and green for the f-block.

  7. Cyclic order - Wikipedia

    en.wikipedia.org/wiki/Cyclic_order

    A cyclic order on a set X with n elements is like an arrangement of X on a clock face, for an n-hour clock. Each element x in X has a "next element" and a "previous element", and taking either successors or predecessors cycles exactly once through the elements as x(1), x(2), ..., x(n). There are a few equivalent ways to state this definition.

  8. Derangement - Wikipedia

    en.wikipedia.org/wiki/Derangement

    Another way to see this is to rename h 1 to h i, where the derangement is more explicit: for any j from 2 to n, P j cannot receive h j. P i receives h 1 . In this case the problem reduces to n − 2 people and n − 2 hats, because P 1 received h i ' s hat and P i received h 1 's hat, effectively putting both out of further consideration.

  9. Hierarchy - Wikipedia

    en.wikipedia.org/wiki/Hierarchy

    The mediaeval scala naturae as a staircase, implying the possibility of progress: [1] Ramon Llull's Ladder of Ascent and Descent of the Mind, 1305. A hierarchy (from Greek: ἱεραρχία, hierarkhia, 'rule of a high priest', from hierarkhes, 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) that are represented as being "above", "below", or ...