Molecule

A molecule is an electrically neutral group of two or more atoms held together by chemical bonds and acting as a single unit. Its atoms have a definite arrangement and composition.

Chemical bond: An interaction that holds atoms or ions together through electrostatic forces and shared or transferred electrons. Molecular atoms are joined by these interactions.
Lewis structure: A diagram representing atoms, bonds, and valence electrons in a molecule or ion. It makes a molecule's bonding pattern and lone pairs visible.
Water: A chemical compound whose molecules each contain two hydrogen atoms bonded to one oxygen atom. Its bent shape and polarity make it a defining example of molecular behavior.
Polyatomic ion: A group of covalently bonded atoms that carries a net electrical charge. Unlike a molecule under this definition, it is not electrically neutral.
Protein: A biological macromolecule made of one or more chains of amino acids. Proteins are large molecules whose structures enable diverse cellular functions.
Covalent bond: A chemical bond formed when atoms share pairs of electrons. Most molecules are built from atoms joined by shared electron pairs.
Molecular orbital theory: A model that describes electrons in molecules as occupying orbitals spread across multiple atoms. It explains bonding through electron states extending over the molecule.
Oxygen: A chemical element that commonly occurs as diatomic molecules, each containing two oxygen atoms. It shows that a molecule can consist of atoms of one element.
Ionic compound: A substance made of positively and negatively charged ions held together by electrostatic attraction. Many ionic solids form extended lattices rather than discrete molecular units.
DNA: A nucleic acid molecule that stores hereditary information in most organisms. Its molecular structure supports information storage and accurate copying.

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