ion

An atom or group of atoms carrying an electric charge by virtue of having gained or lost one or more electrons. Ions charged with negative electricity (anions) travel toward a positive pole (anode); those charged with positive electricity (cations) travel toward a negative pole (cathode). Ions may exist in solid, liquid, or gaseous environments, although those in liquid (electrolytes) are more common and familiar. [G. i., going]

- aquo-i. aquo-i..

- dipolar ions ions possessing both a negative charge and a positive charge, each localized at a different point in the molecule, which thus has both positive and negative “poles”; amino acid s are the most notable dipolar ions, containing a positively charged NH₃⁺ group and a negatively charged COO⁻ group at neutral pH. SYN: amphions, zwitterions.

- gram-i. gram-i..

- hydride i. the H⁻ i., transferred to acceptor molecules in some biologic oxidations.

- hydrogen i. (H⁺) a hydrogen atom minus its electron and therefore carrying a unit positive charge ( i.e., a proton); in water, it combines with a water molecule to form hydronium i., H₃O⁺.

- hydronium i. the hydrated proton, H₃O⁺, a form in which hydrogen i. exists in aqueous solutions; also, H₃O⁺ H₂O, H₃O⁺ 2H₂O, etc. SYN: oxonium i..

- oxonium i. SYN: hydronium i..

- sulfonium i. a compound in which a sulfur atom has three single covalent bonds and therefore has a positive charge analogous to the nitrogen of an ammonium compound; e.g., S-adenosyl-l-methionine.

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ischemic optic neuropathy

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ion 'ī-ən, 'ī-.än n

1) an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons see ANION, CATION

2) a charged subatomic particle (as a free electron)

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n.

an atom or group of atoms that has lost one or more electrons, making it electrically charged and therefore more chemically active. See anion, cation, electrolyte, ionization.

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(iґon) [Gr. iōn going] an atom or radical having a charge of positive (cation) or negative (anion) electricity owing to the loss or gain of one or more electrons. Substances that form ions are called electrolytes. See ionic theory, under theory. ionic adj