Atoms and Molecules

Two fundamental laws govern chemical reactions

Two fundamental laws govern chemical reactions: (1) Law of Conservation of Mass - mass cannot be created or destroyed in chemical reactions, and (2) L

John Dalton proposed that all matter

John Dalton proposed that all matter consists of tiny, indivisible particles called atoms. Key postulates include: atoms are indivisible, atoms of the

Atoms are extremely small particles (radius

Atoms are extremely small particles (radius ~10⁻¹⁰ m) that serve as building blocks of matter. Atomic mass is measured in atomic mass units (u), where

Molecules are groups of atoms held

Molecules are groups of atoms held together by chemical bonds. They can be composed of same elements (like O₂, O₃) or different elements (like H₂O, NH

Ions are charged particles formed when

Ions are charged particles formed when atoms gain or lose electrons. Cations are positively charged (Na⁺), anions are negatively charged (Cl⁻). Polyat