Molekula

Molekula is the smallest unit of a chemical substance that retains the properties of that substance. It is formed when two or more atoms are bound together by chemical bonds. Molecules can belong to elements, such as O2 or N2, which consist of two or more atoms of the same element, or to compounds, such as H2O or CO2, which contain two or more different elements.

Bonding and structure determine a molecule's geometry and behavior. Covalent bonds share electron pairs, while ionic compounds are built from opposite charges in a lattice; molecules can also interact through hydrogen bonding, van der Waals forces, and other non-covalent interactions that influence physical properties such as boiling and melting points.

Molecules vary greatly in size. Simple diatomic molecules contain two atoms, while larger molecules form from many atoms and can include polymers and macromolecules, such as proteins, nucleic acids, and synthetic plastics.

Isomers are molecules with the same chemical formula but different arrangements, leading to different properties. Stereoisomers, constitutional isomers, and conformers illustrate the diversity possible within a single formula.

Quantification and analysis use molar amount and molecular mass. The amount of substance is measured in moles, with one mole containing approximately 6.022 × 10^23 molecules (Avogadro's number). Molecular mass is expressed in atomic mass units (or grams per mole).

In science, molecules are central to chemistry, biology, materials science, and pharmacology, defining the behavior of substances, enabling life processes, and guiding the design of chemicals and drugs.