1. Attraction and Sharing:
* Electronegativity: Atoms with similar electronegativity (the ability to attract electrons) tend to form covalent bonds.
* Valence Electrons: Atoms try to achieve a stable electron configuration, typically by having a full outer shell of electrons (like the noble gases). They achieve this by sharing electrons.
2. Sharing Electrons:
* Covalent Bonds: Atoms share their valence electrons to form a pair of electrons that is attracted to both atomic nuclei. This shared pair creates a covalent bond, holding the atoms together.
* Types of Covalent Bonds:
* Single Bonds: One pair of electrons is shared between the atoms.
* Double Bonds: Two pairs of electrons are shared.
* Triple Bonds: Three pairs of electrons are shared.
3. Molecular Structure:
* Molecular Geometry: The arrangement of atoms in a molecule determines its shape and properties. This geometry is influenced by the number of electron pairs around each atom and the repulsion between these electron pairs.
* Intermolecular Forces: Weak attractions between molecules, such as hydrogen bonding, dipole-dipole forces, and London dispersion forces, influence the physical properties of molecular compounds (melting point, boiling point, etc.).
Examples of Molecular Compounds:
* Water (H₂O): Two hydrogen atoms share electrons with an oxygen atom, forming two single covalent bonds.
* Carbon Dioxide (CO₂): Carbon shares two double bonds with two oxygen atoms.
* Methane (CH₄): Carbon shares a single bond with four hydrogen atoms.
Key Properties of Molecular Compounds:
* Lower Melting and Boiling Points: Covalent bonds are generally weaker than ionic bonds, so molecular compounds tend to have lower melting and boiling points.
* Non-Conductive in Solid and Liquid States: Molecular compounds do not conduct electricity because their electrons are localized within covalent bonds.
* Often Gases or Liquids at Room Temperature: Their weaker bonds allow them to exist in these states.
In summary, molecular compounds form when atoms share electrons to achieve a stable electron configuration. This sharing creates covalent bonds that hold the atoms together in a specific molecular structure with characteristic properties.
