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  2. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows (" periods ") and columns (" groups "). It is an icon of chemistry and is widely used in physics and other sciences. It is a depiction of the periodic law, which states that when the elements are arranged in order ...

  3. Charge number - Wikipedia

    en.wikipedia.org/wiki/Charge_number

    Charges that are positive are called cations. Charges that are negative are called anions. Elements in the same group have the same charge. A group in the periodic table is a term used to represent the vertical columns. The noble gases of the periodic table do not have a charge because they are nonreactive. Noble gases are considered stable ...

  4. List of chemical elements - Wikipedia

    en.wikipedia.org/wiki/List_of_chemical_elements

    List of chemical elements - Wikipedia. List of chemical elements. 118 chemical elements have been identified and named officially by IUPAC. A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ]

  5. Types of periodic tables - Wikipedia

    en.wikipedia.org/wiki/Types_of_periodic_tables

    1971 — Clark, John O. E. periodic table [119] 2005 — Rich's periodic chart exposing diagonal relationships: Non-metals of the left; metals on the right [120] 2018 — Beylkin's periodic table of the elements:4n 2 periods, where n = 2,3..., and shows symmetry, regularity, and elegance, more so than Janet's left step table [121]

  6. Valence (chemistry) - Wikipedia

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

    The valence is the combining capacity of an atom of a given element, determined by the number of hydrogen atoms that it combines with. In methane, carbon has a valence of 4; in ammonia, nitrogen has a valence of 3; in water, oxygen has a valence of 2; and in hydrogen chloride, chlorine has a valence of 1. Chlorine, as it has a valence of one ...

  7. Atomic number - Wikipedia

    en.wikipedia.org/wiki/Atomic_number

    Atomic number is the number of protons, and therefore also the total positive charge, in the atomic nucleus. The Rutherford–Bohr model of the hydrogen atom (Z = 1) or a hydrogen-like ion (Z > 1). In this model, it is an essential feature that the photon energy (or frequency) of the electromagnetic radiation emitted (shown) when an electron ...

  8. Effective nuclear charge - Wikipedia

    en.wikipedia.org/wiki/Effective_nuclear_charge

    It is possible to determine the strength of the nuclear charge by the oxidation number of the atom. Most of the physical and chemical properties of the elements can be explained on the basis of electronic configuration. Consider the behavior of ionization energies in the periodic table. It is known that the magnitude of ionization potential ...

  9. Core electron - Wikipedia

    en.wikipedia.org/wiki/Core_electron

    Core charge is a convenient way of explaining trends in the periodic table. [4] Since the core charge increases as you move across a row of the periodic table , the outer-shell electrons are pulled more and more strongly towards the nucleus and the atomic radius decreases.