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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. 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 ...

  4. List of chemical elements - Wikipedia

    en.wikipedia.org/wiki/List_of_chemical_elements

    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 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...

  5. Charge number - Wikipedia

    en.wikipedia.org/wiki/Charge_number

    Charge number (denoted z) is a quantized and dimensionless quantity derived from electric charge, with the quantum of electric charge being the elementary charge (e, constant). The charge number equals the electric charge (q, in coulombs) divided by the elementary charge: z = q / e. Atomic numbers (Z) are a special case of charge numbers ...

  6. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    An element's atomic number, which is defined as the element's position on the periodic table, is also the number of protons it has in its nucleus. The atomic weight of each element is higher than its proton number, so Rutherford hypothesized that the surplus weight was carried by unknown particles with no electric charge and a mass equal to ...

  7. Chemical element - Wikipedia

    en.wikipedia.org/wiki/Chemical_element

    t. e. A chemical element is a chemical substance that cannot be broken down into other substances by chemical reactions. The basic particle that constitutes a chemical element is the atom. Elements are identified by the number of protons in their nucleus, [ 1 ] known as the element's atomic number. [ 2 ]

  8. Chemical symbol - Wikipedia

    en.wikipedia.org/wiki/Chemical_symbol

    Chemical symbol. The periodic table, elements being denoted by their symbols. Chemical symbols are the abbreviations used in chemistry, mainly for chemical elements; but also for functional groups, chemical compounds, and other entities. Element symbols for chemical elements, also known as atomic symbols, normally consist of one or two letters ...

  9. Glossary of chemistry terms - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_chemistry_terms

    Charge numbers for ions are denoted in superscript (e.g. Na + indicates a sodium ion with a charge number of positive one). Atomic numbers are charge numbers of atomic nuclei. Charles's law When the pressure on a sample of a dry gas is held constant, the Kelvin temperature is directly proportional to its volume. chelating agent chelation