An atom or group of atoms that have a negative electric charge. An "anionic detergent surfactant" is attracted to soil that carries a positive electric charge. Anionic chemicals are mostly used by manufacturers to create foam.
Refers to the chemical ions present that carry a negative charge in contrast to cations, which carry a positive charge. There must be equal amounts of positive and negative charged ions in any water sample. Following are the common anions in their order of decreasing concentration for most lakes: bicarbonate (HCO3-), sulfate (SO4--), chloride (Cl-), carbonate (CO3--), nitrate (NO3-), nitrite (NO2-), and phosphates (H2PO4-, HPO4--, and P04--).
When a salt is dissolved it has two charged molecules: a cation (positively charged) which can behave as an acid and an anion (negatively charged) which can act as a base. If a surface has a positive charge it is called anionic and can be used to capture negatively charged molecules.