Bonding and Structure

• Dot and cross diagrams


  Diagrams used to show the formation of ionic compounds
• Sodium chloride and magnesium oxide are ionic compounds
• Ionic compounds


  • Form when a metal transfers electrons to a non-metal
  • Resulting in the formation of positive and negative ions
• Electron configuration


  The arrangement of electrons in the outer shell of an atom
• The number of protons in the nucleus is the same as the number of electrons in a neutral atom
• Noble gases


  Atoms with a stable electron configuration, used as a reference point for other atoms
• Formation of ionic bonds

  1. Metal atom loses electron(s)

  2. Non-metal atom gains electron(s)

  3. Resulting in positive and negative ions

  4. Ions are attracted by electrostatic forces
• Ionic compounds


  • Sodium chloride
  • Magnesium oxide
• Ions


  • Have the same electron configuration as a noble gas
  • Charge is spread over the whole ion
• Magnesium transfers 2 electrons to oxygen to form ionic bonds
• The ions formed have the same electron configuration as neon
• Ionic compounds


  Form a giant ionic lattice
• Giant ionic lattice


  • Every ion in the lattice is attracted to every other oppositely charged ion
  • Attraction is due to electrostatic forces
• Ionic compounds


  • Have very high melting and boiling points
  • Require a large amount of energy to overcome the strong electrostatic forces of attraction
• Examples of Ionic compounds

  • Sodium chloride (melting point 801°C)
  • Magnesium oxide (melting point 2852°C)
• what effect do Stronger ionic charges have

  Higher melting/boiling points
• Solubility of ionic compounds

  • Soluble in polar solvents like water
  • Water molecules surround the ions, overcoming electrostatic attraction
• Stronger ionic charges effect on solubility


  Decreased solubility
• properties Ionic compounds (as solids)

  • Do not conduct electricity
  • Ions are locked in place by electrostatic forces, cannot move to carry charge
• properties of Ionic compounds (molten or dissolved)

  • Can conduct electricity
  • Ions are now free to move and carry charge
• Ionic compounds are good conductors of electricity when dissolved in water or in a molten state due to the presence of free-moving ions.
• The melting point of an ionic compound is high due to the strong electrostatic forces between oppositely charged ions.
• Ionic compounds are usually solid at room temperature because of their strong ionic bonds.
• Ionic compounds are soluble in water, while covalent compounds may or may not be.
• Ionic compounds tend to have high melting and boiling points due to the strong electrostatic forces between ions.
• Metals with small positive ions tend to form strong ionic bonds as they have high electronegativity differences compared to nonmetals.
• Ionic compounds are soluble in water, while covalent compounds may or may not be.
• Giant ionic lattice


  A three-dimensional arrangement of oppositely charged ions (anions and cations) held together by electrostatic forces. The lattice is called "giant" because it contains a large number of ions and extends in all three dimensions.
• Ions


  Atoms or molecules that have a positive or negative electrical charge due to the loss or gain of electrons. In a giant ionic lattice, each ion is attracted to every other oppositely charged ion due to electrostatic forces.
• Electrostatic forces


  The forces that exist between charged particles. In a giant ionic lattice, the electrostatic forces are responsible for holding the oppositely charged ions together in a stable and rigid lattice structure.
• Covalent bond


  Shared pair of electrons between two non-metal atoms
• Formation of covalent bond

  1. Overlap of atomic orbitals

  2. Sharing of electron pair

  3. Attraction of shared pair to both nuclei
• Covalent bond


  • Both atoms have the same electron configuration as a noble gas
  • Represented by a straight line
• Covalent molecules


  • H2
  • F2
  • HF
• Covalent bonding


  • Atoms share electrons to achieve the same electron configuration as the nearest noble gas
• Exceptions to octet rule: Boron forms 3 covalent bonds, Phosphorus forms 3 or 5 covalent bonds
• Lone pair


  Pair of electrons in the outer shell of an atom that are not used to form covalent bonds
• Expansion of octet


  • Atoms can use d-subshell electrons to form more than 8 electrons in the outer shell
• Molecules with expanded octet

  • PCl5
  • SF6
• Dative covalent bond


  Also called coordinate bond