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  2. Neutron - Wikipedia

    en.wikipedia.org/wiki/Neutron

    The chemical properties of an atom are mostly determined by the configuration of electrons that orbit the atom's heavy nucleus. The electron configuration is determined by the charge of the nucleus, which is determined by the number of protons, or atomic number. The number of neutrons is the neutron number. Neutrons do not affect the electron ...

  3. Atomic radii of the elements (data page) - Wikipedia

    en.wikipedia.org/wiki/Atomic_radii_of_the...

    Just as atomic units are given in terms of the atomic mass unit (approximately the proton mass), the physically appropriate unit of length here is the Bohr radius, which is the radius of a hydrogen atom. The Bohr radius is consequently known as the "atomic unit of length". It is often denoted by a 0 and is approximately 53 pm. Hence, the values ...

  4. History of atomic theory - Wikipedia

    en.wikipedia.org/wiki/History_of_atomic_theory

    The current theoretical model of the atom involves a dense nucleus surrounded by a probabilistic "cloud" of electrons. Atomic theory is the scientific theory that matter is composed of particles called atoms. The definition of the word "atom" has changed over the years in response to scientific discoveries.

  5. Atomicity (chemistry) - Wikipedia

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

    Atomicity is the total number of atoms present in a molecule of an element. For example, each molecule of oxygen (O 2) is composed of two oxygen atoms.Therefore, the atomicity of oxygen is 2.

  6. Quantum mechanics - Wikipedia

    en.wikipedia.org/wiki/Quantum_mechanics

    Quantum mechanics is a fundamental theory that describes the behavior of nature at and below the scale of atoms. [2]: 1.1 It is the foundation of all quantum physics, which includes quantum chemistry, quantum field theory, quantum technology, and quantum information science.

  7. Atomic ratio - Wikipedia

    en.wikipedia.org/wiki/Atomic_ratio

    The atomic ratio is a measure of the ratio of atoms of one kind (i) to another kind (j). A closely related concept is the atomic percent (or at.%), which gives the percentage of one kind of atom relative to the total number of atoms. [1]

  8. Relative atomic mass - Wikipedia

    en.wikipedia.org/wiki/Relative_atomic_mass

    Here the "unified atomic mass unit" refers to 1/12 of the mass of an atom of 12 C in its ground state. [13] The IUPAC definition [1] of relative atomic mass is: An atomic weight (relative atomic mass) of an element from a specified source is the ratio of the average mass per atom of the element to 1/12 of the mass of an atom of 12 C.

  9. Ununennium - Wikipedia

    en.wikipedia.org/wiki/Ununennium

    This is an accepted version of this page This is the latest accepted revision, reviewed on 28 January 2025. Hypothetical chemical element, symbol Uue and atomic number 119 Chemical element with atomic number 119 (Uue) Ununennium, 119 Uue Theoretical element Ununennium Pronunciation / ˌ uː n. uː n ˈ ɛ n i ə m / ⓘ (OON -oon- EN -ee-əm) Alternative names element 119, eka-francium ...