Bonding and Structures

• Covalent molecular crystals


  Contain individual molecules in a pattern within the crystal lattice
• Covalent molecular structure bonds

  • Atoms within each molecule are bonded covalently
  • Forces between each molecule involve weak intermolecular attractions
• Covalent molecular crystal example

  • NH3
• Covalent bond


  Formed between atoms that have similar electronegativities. This bond shares the electrons.
• Hydrogen bond


  Is an intermolecular force that occurs between a hydrogen atom in a molecule to an electronegative atom including O, F and N in another molecule.
• Polar covalent bond formed with atoms of slightly different electronegativities. This is between 0.4 and 1.8. The molecule could have slightly positive or slightly negative ends.
• What is Metallic bonding? 


  Consist of metal cations surrounded by a "sea" of mobile valence electrons
• These delocalized electrons are capable of moving throughout the entire crystal
• As a result, metals are good conductors of electricity
• Metallic crystals have higher melting point and boiling points because they bonds are harder to break.
• Intra-


  Inside the molecules
• Inter-


  Between molecules
• Dipole-dipole forces


  Forces that occur when two polar molecules are attracted to each other because of their opposite charges.
• London dispersion forces

  Weak forces that occur between nonpolar molecules. They result from the temporary, instantaneous polarization of the electron clouds in the molecules.
• Covalent molecular crystals


  A type of crystal made up of individual molecules that are held together by covalent bonds and arranged in a repeating pattern within the crystal lattice. The molecules are held together in the crystal by intermolecular forces such as dipole-dipole or London dispersion forces.
• Intermolecular forces


  The forces that hold molecules together in a solid crystal. These forces include ion-dipole forces, dipole-dipole forces, and London dispersion forces.
• Highly electronegative atom


  An atom that attracts electrons strongly, such as nitrogen, oxygen, or fluorine
• Hydrogen bonding


  A type of intermolecular force that occurs when a hydrogen atom is bonded to a highly electronegative atom and forms a weak attraction with a lone pair of electrons on another electronegative atom
• Partially positive hydrogen atom

  A hydrogen atom that has a slightly positive charge due to the electronegativity of the atom it is bonded to.
• why are hydrogen bonds strong? 


  Hydrogen bonds are stong intermolecular forces because of the small atomic radius of the Hydrogen and the high electronegativity of another atom.