gasses
he only chemical elements which are stable multi atom homonuclear molecules at standard temperature and pressure (STP), are hydrogen (H2), nitrogen (N2) and oxygen (O2); plus two halogens, fluorine (F2) and chlorine (Cl2). These gases, when grouped together with the monatomic noble gases; which are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn) ; are called "elemental gases". Alternatively they are sometimes known as "molecular gases" to distinguish them from molecules that are also chemical compounds.
Etymology
The word gas is a neologism first used by the early 17th-century Flemish chemist J.B. Van Helmont.[4] Van Helmont's word appears to have been simply a phonetic transcription of the Greek word χάος Chaos – the g in Dutch being pronounced like ch in "loch" – in which case Van Helmont was simply following the established alchemical usage first attested in the works of Paracelsus. According to Paracelsus's terminology, chaos meant something like "ultra-rarefied water".[5]
An alternative story[6] is that Van Helmont's word is corrupted from gahst (or geist), signifying a ghost or spirit. This was because certain gases suggested a supernatural origin, such as from their ability to cause death, extinguish flames, and to occur in "mines, bottom of wells, churchyards and other lonely places".
Physical characteristics
Drifting smoke particles provide clues to the movement of the surrounding gas.
As most gases are difficult to observe directly, they are described through the use of four physical properties or macroscopic characteristics: pressure, volume, number of particles (chemists group them by moles) and temperature. These four characteristics were repeatedly observed by scientists such as Robert Boyle, Jacques Charles, John Dalton, Joseph Gay-Lussac and Amedeo Avogadro for a variety of gases in various settings. Their detailed studies ultimately led to a mathematical relationship among these properties expressed by the
Etymology
The word gas is a neologism first used by the early 17th-century Flemish chemist J.B. Van Helmont.[4] Van Helmont's word appears to have been simply a phonetic transcription of the Greek word χάος Chaos – the g in Dutch being pronounced like ch in "loch" – in which case Van Helmont was simply following the established alchemical usage first attested in the works of Paracelsus. According to Paracelsus's terminology, chaos meant something like "ultra-rarefied water".[5]
An alternative story[6] is that Van Helmont's word is corrupted from gahst (or geist), signifying a ghost or spirit. This was because certain gases suggested a supernatural origin, such as from their ability to cause death, extinguish flames, and to occur in "mines, bottom of wells, churchyards and other lonely places".
Physical characteristics
Drifting smoke particles provide clues to the movement of the surrounding gas.
As most gases are difficult to observe directly, they are described through the use of four physical properties or macroscopic characteristics: pressure, volume, number of particles (chemists group them by moles) and temperature. These four characteristics were repeatedly observed by scientists such as Robert Boyle, Jacques Charles, John Dalton, Joseph Gay-Lussac and Amedeo Avogadro for a variety of gases in various settings. Their detailed studies ultimately led to a mathematical relationship among these properties expressed by the