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How do atoms combine to form molecules?
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The Bohr model describes the structure of atoms, in this case hydrogen.
Atoms combine to form molecules primarily through the interaction of their outermost electrons, known as valence electrons. These interactions allow atoms to achieve a more stable, lower-energy state. There are three fundamental ways these electrons facilitate bonding:12
- Ionic Bonding: One atom transfers one or more valence electrons to another. This creates oppositely charged ions that are held together by the electrostatic force of attraction.13
- Covalent Bonding: Atoms share pairs of valence electrons. In this arrangement, the shared electrons effectively link the nuclei of the atoms together, forming a molecule. While simple models treat these as localized pairs, molecular-orbital theory describes these electrons as being distributed over the atoms in the molecule.13
- Metallic Bonding: In certain materials, valence electrons are shared among all atoms, creating a "sea" of electrons in which positive ions are suspended.1
Additionally, atoms and molecules can interact through weaker forces, such as polar attractions, hydrogen bonds, and van der Waals forces, which do not involve the direct exchange or sharing of electrons in the same manner as primary chemical bonds.1