Bonding

• Ionic bonding


  Occurs between a metal and a non-metal, electrons are transferred from the metal to the non-metal to achieve full outer shells
• Ions


  Charged particles formed when electrons are transferred
• Ionic lattice


  Oppositely charged ions attract through electrostatic forces to form a giant ionic lattice
• Covalent bonding


  Occurs between two non-metals, electrons are shared between the two outer shells in order to achieve a full outer shell
• Multiple covalent bonds


  Multiple electron pairs can be shared to produce multiple covalent bonds
• Dot and cross diagrams


  Used to represent the shared electron pairs in covalent bonds

  
• Dative bonding


  Occurs when both of the electrons in the shared pair are supplied from a single atom, indicated using an arrow from the lone electron pair
• Metallic bonding


  Consists of a lattice of positively charged ions surrounded by a 'sea' of delocalised electrons, producing a strong electrostatic force of attraction
• The greater the charge on the positive ion


  The stronger the attractive force as more electrons are released into the 'sea'
• Ions that are larger in size

  Produce a weaker attraction due to their greater atomic radius
• Physical properties


  Include the boiling point, melting point, solubility and conductivity, and are different depending on the type of bonding and the crystal structure
• Main types of crystal structure

  • Ionic
  • Metallic
  • Simple molecular
  • Macromolecular
• Ionic crystal structure


  • High melting and boiling point, can conduct electricity when molten or in solution, brittle
• Metallic structure


  • Good conductors, malleable, high melting points, nearly always solid at room temperature
• Simple molecular structure


  • Consist of covalently bonded molecules held together with weak van der waals forces, have low melting and boiling points, very poor conductors
• Macromolecular structure


  • Covalently bonded into a giant lattice structure, have very high melting points, rigid

  
• Electron pairs


  Determine the shape of a molecule, each pair naturally repels each other so that the largest bond angle possible exists between the covalent bonds

  
• Lone pair repulsion


  Lone pairs provide additional repulsive forces, reducing the bond angle between covalent bonds by 2.5 degrees for every lone pair present
• Common molecule shapes


  • Linear
  • V-shaped
  • Trigonal planar
  • Triangular pyramid
  • Tetrahedral
  • Trigonal bipyramid
  • Octahedral
• Electronegativity


  The power of an atom to attract negative charge towards itself within a covalent bond, increases along a period and decreases down a group
• Permanent dipole


  Formed when the two atoms in a covalent bond have different electronegativities, the more electronegative atom draws more of the negative charge towards itself
• Induced dipole


  Can form when the electron orbitals around a molecule are influenced by another charged particle
• Van der Waals forces

  The weakest type of intermolecular force, acts as an induced dipole between molecules
• The larger the Mr of the molecule


  The stronger the van der waals forces
• Straight chain molecules


  Experience stronger van der waals forces than branched chain molecules as they can line up and pack closer together
• Permanent dipole


  Type of intermolecular force that acts between molecules with a polar bond, the δ+ and δ- regions attract each other
• Hydrogen bonding


  The strongest type of intermolecular force, forms between hydrogen and the three most electronegative atoms: nitrogen, oxygen and fluorine

  
• Molecules held together with hydrogen bonds

  Have much higher melting and boiling points compared to similar sized molecules without hydrogen bonding
• What is the "sea of electrons" relevant to?

  It's relevant to the attraction between positive ions (cations) and surrounding electrons, where the more electrons in the sea, the stronger the attractive force.
• What is a positive ion?

  A positive ion, also known as a cation, is an atom or group of atoms that has lost one or more electrons, resulting in a positive charge.