Poliatomi

Poliatomi is a term used in chemistry to describe species composed of more than one atom that are bound together to function as a single unit. In English, the corresponding term is polyatomic. Poliatomi include both neutral molecules and charged ions, known as polyatomic ions.

Examples of neutral polyatomic molecules include water (H2O), carbon dioxide (CO2), ammonia (NH3), and methane (CH4). Polyatomic ions include nitrate (NO3−), carbonate (CO3^2−), sulfate (SO4^2−), and ammonium (NH4+). These species form through covalent bonding, where atoms share electron pairs to achieve stable electron configurations.

The structure of poliatomi is often described by VSEPR theory, which predicts three-dimensional geometries based on electron-pair repulsion. The arrangement of atoms determines molecular polarity, reactivity, and physical properties such as boiling and melting points. Some poliatomi are nonpolar, while many are polar due to asymmetrical shapes and unequal distribution of charge.

Poliatomi play central roles in numerous chemical contexts. They can participate in reactions as discrete units, or they can combine with counter-ions to form salts. Polyatomic ions, in particular, influence acid–base chemistry, solubility, and electrostatic interactions in solutions.

In notation, poliatomi units are often written as part of a formula with parentheses when they appear as a subunit, for example (NH4)+ in ammonium salts, or (NO3)− in nitrates. Understanding poliatomi helps explain the behavior of many compounds encountered in chemistry, biology, and environmental science.