Covalent bonding

• Covalent bonding is the electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

  
• How atoms form covalent bonds (Dot and cross & Electron configuration)

  • Atoms use unpaired electrons in the orbitals to form covalent bonds.
  • The unpaired electron in the orbital of one atom can be shared with an unpaired electron in the orbital of another atom
  • Atom can promote electrons into unoccupied orbital in the same energy level to form more covalent bonds. (EC)
  • May not promote electron in some cases like PCl3 and PCl5.
• Covalent bonding has:

  • Low melting point because only weak intermolecular bonds between the separate molecules have to be broken
  • Low conductivity as there are no freely moving charge carriers
• Dative covalent bond is a bond in which two atoms share a pair of electrons but one atom provides both electrons.
• Covalent bond can be soluble in a 'like dissolve like '. Covalent compound are non-polar and hence tend to be soluble in non-polar solvent like hexane.
• Molecular Covalent Crystalline Substances exist as single molecules, exist as gas, liquid, or melting point solids.

  Many of the solid molecular covalent substances form crystalline structures which are called Molecular Covalent Crystals

  • Low melting point
  • brittle because they don't have strong bonds like ionic crystals for diamond
  • Do not conduct electricity as there are no charge for them to carry
• Molecular Covalent Crystals: Iodine

  • Pack together into a regular arrangement causing the crystalline form of Iodine

  
• Molecular Covalent Crystals: Ice

  • A molecule of water is arranged in a regular arrangement forming a crystalline structure.