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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. [101] In astrophysics, neutral hydrogen in the interstellar medium is called H I and ionized hydrogen is called H II. [102] Radiation from stars ionizes H I to H II, creating spheres of ionized H II ...
Chemical symbols are the abbreviations used in chemistry, mainly for chemical elements; but also for functional groups, chemical compounds, and other entities. Element symbols for chemical elements, also known as atomic symbols, normally consist of one or two letters from the Latin alphabet and are written with the first letter capitalised.
A mnemonic is a memory aid used to improve long-term memory and make the process of consolidation easier. Many chemistry aspects, rules, names of compounds, sequences of elements, their reactivity, etc., can be easily and efficiently memorized with the help of mnemonics.
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).
Also acid ionization constant or acidity constant. A quantitative measure of the strength of an acid in solution expressed as an equilibrium constant for a chemical dissociation reaction in the context of acid-base reactions. It is often given as its base-10 cologarithm, p K a. acid–base extraction A chemical reaction in which chemical species are separated from other acids and bases. acid ...
In modern chemistry, the p stands for "the negative decimal logarithm of", and is used in the term pK a for acid dissociation constants, [11] so pH is "the negative decimal logarithm of H + ion concentration", while pOH is "the negative decimal logarithm of OH − ion concentration".
Quantity (common name/s) (Common) symbol/s Defining equation SI unit Dimension Temperature gradient: No standard symbol K⋅m −1: ΘL −1: Thermal conduction rate, thermal current, thermal/heat flux, thermal power transfer
henry (H) luminosity: watt (W) Lagrangian: joule (J) Lagrangian density: joule per cubic meter (J/m 3) length: meter (m) ℓ: azimuthal quantum number: unitless magnetization: ampere per meter (A/m) moment of force often simply called moment or torque newton meter (N⋅m)