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  2. Actinium - Wikipedia

    en.wikipedia.org/wiki/Actinium

    Actinium is a chemical element; it has symbol Ac and atomic number 89. It was first isolated by Friedrich Oskar Giesel in 1902, who gave it the name emanium; the element got its name by being wrongly identified with a substance André-Louis Debierne found in 1899 and called actinium.

  3. 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 ...

  4. Actinide - Wikipedia

    en.wikipedia.org/wiki/Actinide

    The actinide (/ ˈ æ k t ɪ n aɪ d /) or actinoid (/ ˈ æ k t ɪ n ɔɪ d /) series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium. Number 103, lawrencium, is also generally included despite being part of the 6d transition series. The actinide series ...

  5. List of elements by atomic properties - Wikipedia

    en.wikipedia.org/wiki/List_of_elements_by_atomic...

    This is a list of chemical elements and their atomic properties, ordered by atomic number (Z). ... 0.89: 5.2117: 215 — 198: 2 57 ... a few atomic radii are ...

  6. Isotopes of actinium - Wikipedia

    en.wikipedia.org/wiki/Isotopes_of_actinium

    Actinium (89 Ac) has no stable isotopes and no characteristic terrestrial isotopic composition, thus a standard atomic weight cannot be given. There are 34 known isotopes, from 203 Ac to 236 Ac, and 7 isomers.

  7. Atomic number - Wikipedia

    en.wikipedia.org/wiki/Atomic_number

    The atomic number or nuclear charge number (symbol Z) of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons , this is equal to the proton number ( n p ) or the number of protons found in the nucleus of every atom of that element.

  8. Chemical element - Wikipedia

    en.wikipedia.org/wiki/Chemical_element

    Atomic number, Element, and Symbol all serve independently as unique identifiers. ... 0.89: 336.53: 1032: 0.757: 0.82: 20 900: primordial solid 20 Ca Calcium [ae] 2 4 ...

  9. Neutron - Wikipedia

    en.wikipedia.org/wiki/Neutron

    An atomic nucleus is formed by a number of protons, Z (the atomic number), and a number of neutrons, N (the neutron number), bound together by the nuclear force. Protons and neutrons each have a mass of approximately one dalton. The atomic number determines the chemical properties of the atom, and the neutron number determines the isotope or ...