A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. It represents the smallest fundamental unit of a chemical compound that retains the chemical properties of that specific substance.
**Core Characteristics:** * **Composition:** Built from atoms of the same element (e.g., oxygen gas, O₂) or different elements (e.g., water, H₂O). * **Bonding:** Atoms are typically connected via covalent bonds, which involve the sharing of electrons. * **Charge:** Molecules carry no net electrical charge, which distinguishes them from polyatomic ions.
**Primary Classifications:** * **Diatomic Molecules:** Composed of exactly two atoms (e.g., Carbon monoxide, CO; Nitrogen gas, N₂). * **Polyatomic Molecules:** Composed of more than two atoms (e.g., Carbon dioxide, CO₂; Glucose, C₆H₁₂O₆). * **Macromolecules:** Extremely large molecules containing thousands to millions of atoms (e.g., DNA, proteins, synthetic polymers).