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
• When electrons are transferred, it creates charged particles called ions
• Oppositely charged ions attract through electrostatic forces to form a giant ionic lattice
• Common compound ions include:

  • Sulfate: SO4^2-
  • Hydroxide: OH-
  • Nitrate: NO3-
  • Carbonate: CO3^2-
  • Ammonium: NH4+
• Covalent bonds form between two non-metals
• Electrons are shared between the two outer shells to achieve a full outer shell
• Multiple electron pairs can be shared to produce multiple covalent bonds
• Dative or coordinate bonds form when both electrons in the shared pair are supplied from a single atom
• Once a dative bond has formed, it is treated as a standard covalent bond
• Metallic bonding consists of a lattice of positively charged ions surrounded by a ‘sea’ of delocalised electrons
• Greater charge on the positive ion leads to a stronger attractive force
• Ions that are larger in size produce a weaker attraction due to their greater atomic radius
• Physical properties of a substance include boiling point, melting point, solubility, and conductivity
• Different physical properties depend on the type of bonding and the crystal structure of the compound
• There are four main types of crystal structure: ionic, metallic, simple molecular, and macromolecular
• Substances with an ionic crystal structure have a high melting and boiling point
• Ionic substances can conduct electricity when molten or in solution
• Ionic substances are often brittle materials
• Substances with metallic structure are often good conductors
• Metals are malleable and have high melting points
• Mercury is the only liquid metal at room temperature
• Substances with a simple molecular structure have low melting and boiling points
• Simple molecular substances are very poor conductors
• Substances with a macromolecular structure have a very high melting point
• Diamond is one of the hardest, strongest materials known
• Graphite can conduct electricity due to free electrons moving between layers
• The shape of a molecule is determined by the number of electron pairs around the central atom
• Lone pairs present around the central atom and change the bond angle
• Molecule shapes are determined by the type and quantity of electron pairs
• Common molecule shapes include:

  • Linear: 180°
  • Bent: 104.5°
  • Trigonal Planar: 120°
  • Triangular Pyramid: 107°
  • Tetrahedral: 109.5°
  • Trigonal Bipyramid: 90° and 120°
  • Octahedral: 90°
• The negative charge around a covalent bond is not evenly spread around the orbitals of the bonded atoms
• Electronegativity increases along a period and decreases down a group
• If two atoms have different electronegativities, a polar bond forms
• Polar molecules with a permanent dipole can align to form a lattice of molecules
• There are three main types of intermolecular force: Van der Waals Forces, Permanent Dipole, and Hydrogen Bonding
• Van der Waals Forces are the weakest type of intermolecular force
• Permanent Dipole acts between molecules with a polar bond
• Hydrogen Bonding is the strongest type of intermolecular force
• Hydrogen bonds form between hydrogen and nitrogen, oxygen, or fluorine