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  2. Helium compounds - Wikipedia

    en.wikipedia.org/wiki/Helium_compounds

    Helium is the smallest and the lightest noble gas and one of the most unreactive elements, so it was commonly considered that helium compounds cannot exist at all, or at least under normal conditions. [1] Helium's first ionization energy of 24.57 eV is the highest of any element. [2]

  3. Chemically inert - Wikipedia

    en.wikipedia.org/wiki/Chemically_inert

    The noble gases (helium, neon, argon, krypton, xenon and radon) were previously known as 'inert gases' because of their perceived lack of participation in any chemical reactions. The reason for this is that their outermost electron shells (valence shells) are completely filled, so that they have little tendency to gain or lose electrons.

  4. Combustibility and flammability - Wikipedia

    en.wikipedia.org/wiki/Combustibility_and...

    A more recent industrial standard is the European EN 13501-1 - Fire classification of construction products and building elements—which roughly replaces A2 with A2/B, B1 with C, B2 with D/E and B3 with F. B3 or F rated materials may not be used in building unless combined with another material that reduces the flammability of those materials.

  5. Helium - Wikipedia

    en.wikipedia.org/wiki/Helium

    The Rollin film also covers the interior of the larger container; if it were not sealed, the helium II would creep out and escape. [30] Helium II is a superfluid, a quantum mechanical state of matter with strange properties. For example, when it flows through capillaries as thin as 10 to 100 nm it has no measurable viscosity. [28]

  6. List of gases - Wikipedia

    en.wikipedia.org/wiki/List_of_gases

    List [ edit ] This list is sorted by boiling point of gases in ascending order, but can be sorted on different values. "sub" and "triple" refer to the sublimation point and the triple point , which are given in the case of a substance that sublimes at 1 atm; "dec" refers to decomposition . "~" means approximately.

  7. List of chemical elements - Wikipedia

    en.wikipedia.org/wiki/List_of_chemical_elements

    118 chemical elements have been identified and named officially by IUPAC.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).

  8. List of alternative nonmetal classes - Wikipedia

    en.wikipedia.org/wiki/List_of_alternative...

    The nonmetallic elements are sometimes instead divided into two to seven alternative classes or sets according to, for example, electronegativity; the relative homogeneity of the halogens; molecular structure; the peculiar nature of hydrogen; the corrosive nature of oxygen and the halogens; their respective groups; and variations thereupon.

  9. List of states of matter - Wikipedia

    en.wikipedia.org/wiki/List_of_states_of_matter

    Quasicrystal: A solid in which the positions of the atoms have long-range order, but this is not in a repeating pattern. Different structural phases of polymorphic materials are considered to be different states of matter in the Landau theory. For an example, see Ice § Phases. Liquid: A mostly non-compressible fluid. Able to conform to the ...