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Hydrogen, as atomic H, is the most abundant chemical element in the universe, making up 75% of normal matter by mass and >90% by number of atoms. [96] In astrophysics, neutral hydrogen in the interstellar medium is called H I and ionized hydrogen is called H II. [97] Radiation from stars ionizes H I to H II, creating spheres of ionized H II ...
Depiction of a hydrogen atom showing the diameter as about twice the Bohr model radius. (Image not to scale) A hydrogen atom is an atom of the chemical element hydrogen.The electrically neutral hydrogen atom contains a single positively charged proton in the nucleus, and a single negatively charged electron bound to the nucleus by the Coulomb force.
H/O: history of ... HOB: head of bed (usually followed by number of degrees of elevation, e.g., HOB 10°) HOCM: hypertrophic obstructive cardiomyopathy: HONK: hyperosmolar nonketotic state HOPI: History of present illness: H&P: history and physical examination (which very often are considered as a pair) HPA: hypothalamic-pituitary-adrenal axis ...
In chemistry, the hydron, informally called proton, [2] is the cationic form of atomic hydrogen, represented with the symbol H +The general term "hydron", endorsed by IUPAC, encompasses cations of hydrogen regardless of isotope: thus it refers collectively to protons (1 H +) for the protium isotope, deuterons (2 H + or D +) for the deuterium isotope, and tritons (3 H + or T +) for the tritium ...
3. Between two groups, may mean that the first one is a proper subgroup of the second one. > (greater-than sign) 1. Strict inequality between two numbers; means and is read as "greater than". 2. Commonly used for denoting any strict order. 3. Between two groups, may mean that the second one is a proper subgroup of the first one. ≤ 1.
a.c.h.s., ac&hs ante cibum et hora somni: before meals and at bedtime a.d. auris dextra: right ear a single-storey a can be mistaken as an o which could read "o.d.", meaning right eye ad., add. adde addatur: add let there be added ad lib. ad libitum: Latin, "at one's pleasure"; as much as one desires; freely
Hecto (symbol: h) is a decimal unit prefix in the metric system denoting a factor of one hundred. It was adopted as a multiplier in 1795, and comes from the Greek ἑκατόν hekatón, meaning "hundred". In 19th century English it was sometimes spelled "hecato", in line with a puristic opinion by Thomas Young.
H-phrases Physical Hazards [5] Code Phrase H200: Unstable explosive H201: Explosive: mass explosion hazard H202: Explosive: severe projection hazard H203: Explosive: fire, blast or projection hazard H204: Fire or projection hazard H205: May mass explode in fire H206: Fire, blast or projection hazard: increased risk of explosion if desensitizing ...