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  2. Atomic nucleus - Wikipedia

    en.wikipedia.org/wiki/Atomic_nucleus

    The diameter of the nucleus is in the range of 1.70 fm (1.70 × 10 −15 m [7]) for hydrogen (the diameter of a single proton) to about 11.7 fm for uranium. [8] These dimensions are much smaller than the diameter of the atom itself (nucleus + electron cloud), by a factor of about 26,634 (uranium atomic radius is about 156 pm ( 156 × 10 −12 m ...

  3. 1,2,4-Triazole - Wikipedia

    en.wikipedia.org/wiki/1,2,4-Triazole

    1,2,4-Triazole (as ligand in coordination compounds, Htrz abbreviation is sometimes used) is one of a pair of isomeric chemical compounds with molecular formula C 2 H 3 N 3, called triazoles, which have a five-membered ring of two carbon atoms and three nitrogen atoms. 1,2,4-Triazole and its derivatives find use in a wide variety of applications.

  4. Exotic atom - Wikipedia

    en.wikipedia.org/wiki/Exotic_atom

    A hadronic atom is an atom in which one or more of the orbital electrons are replaced by a negatively charged hadron. [8] Possible hadrons include mesons such as the pion or kaon, yielding a pionic atom [9] or a kaonic atom (see Kaonic hydrogen), collectively called mesonic atoms; antiprotons, yielding an antiprotonic atom; and the Σ −

  5. 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.

  6. Urelement - Wikipedia

    en.wikipedia.org/wiki/Urelement

    The Zermelo set theory of 1908 included urelements, and hence is a version now called ZFA or ZFCA (i.e. ZFA with axiom of choice). [1] It was soon realized that in the context of this and closely related axiomatic set theories, the urelements were not needed because they can easily be modeled in a set theory without urelements. [2]

  7. Rydberg atom - Wikipedia

    en.wikipedia.org/wiki/Rydberg_atom

    A comparison of the potential in a hydrogen atom with that in a Rydberg state of a different atom. A large core polarizability has been used in order to make the effect clear. The black curve is the Coulombic 1/r potential of the hydrogen atom while the dashed red curve includes the 1/r 4 term due to polarization of the ion core.

  8. Atomic number - Wikipedia

    en.wikipedia.org/wiki/Atomic_number

    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 jumps from one orbital to another be proportional to the mathematical square of atomic charge (Z 2).

  9. Nitrogen - Wikipedia

    en.wikipedia.org/wiki/Nitrogen

    A few mixed halides and hydrohalides are known, but are mostly unstable; examples include NClF 2, NCl 2 F, NBrF 2, NF 2 H, NFH 2, NCl 2 H, and NClH 2. [ 61 ] Nitrogen trifluoride (NF 3 , first prepared in 1928) is a colourless and odourless gas that is thermodynamically stable, and most readily produced by the electrolysis of molten ammonium ...