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Polyatomic ions often are useful in the context of acid–base chemistry and in the formation of salts. Often, a polyatomic ion can be considered as the conjugate acid or base of a neutral molecule. For example, the conjugate base of sulfuric acid (H 2 SO 4) is the polyatomic hydrogen sulfate anion (HSO − 4).
Ions consisting of only a single atom are termed atomic or monatomic ions, while two or more atoms form molecular ions or polyatomic ions. In the case of physical ionization in a fluid (gas or liquid), "ion pairs" are created by spontaneous molecule collisions, where each generated pair consists of a free electron and a positive ion. [5]
Cations are positively (+) charged ions while anions are negatively (−) charged. This can be remembered with the help of the following mnemonics. Cats have paws ⇔ Cations are pawsitive. [23] Ca+ion: The letter t in cation looks like a + (plus) sign. [24] An anion is a negative ion. (An egative ion ⇒ Anion). [25]
It is a polyatomic anion with the chemical formula H C O − 3. Bicarbonate serves a crucial biochemical role in the physiological pH buffering system. [3] The term "bicarbonate" was coined in 1814 by the English chemist William Hyde Wollaston. [4] [5] The name lives on as a trivial name.
Individual ions within a salt usually have multiple near neighbours, so they are not considered to be part of molecules, but instead part of a continuous three-dimensional network. Salts usually form crystalline structures when solid. Salts composed of small ions typically have high melting and boiling points, and are hard and brittle.
Structure of the orthosilicate anion SiO 4− 4. A silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula [SiO (4-2x)− 4−x] n, where 0 ≤ x < 2. The family includes orthosilicate SiO 4− 4 (x = 0), metasilicate SiO 2− 3 (x = 1), and pyrosilicate Si 2 O 6− 7 (x = 0.5 ...
The cation is always named first. Ions can be metals, non-metals or polyatomic ions. Therefore, the name of the metal or positive polyatomic ion is followed by the name of the non-metal or negative polyatomic ion. The positive ion retains its element name whereas for a single non-metal anion the ending is changed to -ide.
Polyatomic ions may sometimes be usefully thought of as electrically charged molecules. The term unstable molecule is used for very reactive species, i.e., short-lived assemblies ( resonances ) of electrons and nuclei , such as radicals , molecular ions , Rydberg molecules , transition states , van der Waals complexes , or systems of colliding ...