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  2. Multiplicity (chemistry) - Wikipedia

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

    When S > L there are only 2L+1 orientations of total angular momentum possible, ranging from S+L to S-L. [2] [3] The ground state of the nitrogen atom is a 4 S state, for which 2S + 1 = 4 in a quartet state, S = 3/2 due to three unpaired electrons. For an S state, L = 0 so that J can only be 3/2 and there is only one level even though the ...

  3. 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]

  4. Atom (order theory) - Wikipedia

    en.wikipedia.org/wiki/Atom_(order_theory)

    In the mathematical field of order theory, an element a of a partially ordered set with least element 0 is an atom if 0 < a and there is no x such that 0 < x < a. Equivalently, one may define an atom to be an element that is minimal among the non-zero elements, or alternatively an element that covers the least element 0 .

  5. Atom (measure theory) - Wikipedia

    en.wikipedia.org/wiki/Atom_(measure_theory)

    Given a measurable space (,) and a measure on that space, a set in is called an atom if > and for any measurable subset , either () = or () = (). [ 1 ] The equivalence class of A {\displaystyle A} is defined by [ A ] := { B ∈ Σ : μ ( A Δ B ) = 0 } , {\displaystyle [A]:=\{B\in \Sigma :\mu (A\Delta B)=0\},} where Δ {\displaystyle \Delta ...

  6. Urelement - Wikipedia

    en.wikipedia.org/wiki/Urelement

    In type theory, an object of type 0 can be called an urelement; hence the name "atom". Adding urelements to the system New Foundations (NF) to produce NFU has surprising consequences. In particular, Jensen proved [ 5 ] the consistency of NFU relative to Peano arithmetic ; meanwhile, the consistency of NF relative to anything remains an open ...

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

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

    Note: All measurements given are in picometers (pm). For more recent data on covalent radii see Covalent radius.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.

  8. Atoms in molecules - Wikipedia

    en.wikipedia.org/wiki/Atoms_in_molecules

    In quantum chemistry, the quantum theory of atoms in molecules (QTAIM), sometimes referred to as atoms in molecules (AIM), is a model of molecular and condensed matter electronic systems (such as crystals) in which the principal objects of molecular structure - atoms and bonds - are natural expressions of a system's observable electron density distribution function.

  9. Atomic mass - Wikipedia

    en.wikipedia.org/wiki/Atomic_mass

    Alternately, the atomic mass of a carbon-12 atom may be expressed in any other mass units: for example, the atomic mass of a carbon-12 atom is 1.992 646 882 70 (62) × 10 −26 kg. As is the case for the related atomic mass when expressed in daltons , the relative isotopic mass numbers of nuclides other than carbon-12 are not whole numbers, but ...