In chemistry and physics, the Loschmidt number is the number density of an ideal gas at standard temperature and pressure, Chemistry (from Greek χημεία khemeia meaning alchemy, see below for possible origins of this word) is the science of matter at the atomic to molecular scale, dealing primarily with collections of atoms (such as molecules, crystals, and metals). ... The first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density. ... An ideal gas or perfect gas is a hypothetical gas consisting of identical particles of negligible volume, with no intermolecular forces. ... Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ...

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It is named after the Austrian chemist Johann Josef Loschmidt, who calculated, in 1865, the number of molecules of such a gas in one cubic centimeter. Johann Josef Loschmidt (March 15, 1821 - July 8, 1895) was an Austrian physicist and chemist. ... 1865 (MDCCCLXV) is a common year starting on Sunday. ...

It is also used as synonym for Avogadro's constant; this use is considered archaic in English language, while it is still current in other languages, e.g. in German scientific literature and textbooks. Avogadros number, also called Avogadros constant (NA) is a large constant used in chemistry and physics. ... Adjective archaic (more archaic, most archaic) From an earlier period and no longer in common use; of or characterized by antiquity or archaism, antiquated. ...