Search results
Results from the WOW.Com Content Network
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]
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.
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.
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]
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.
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).
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.
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 ...