Physics and math tutor flashcards

• The 3 main types of chemical bonds are:

  • Ionic
  • Covalent
  • Metallic
• Ionic bonding is the electrostatic attraction between positive and negative ions
• An example of an ionically bonded substance is NaCl (Sodium Chloride - salt)
• Covalent bonding is the electrostatic attraction between a shared pair of electrons and the nuclei
• Metallic bonding is the electrostatic attraction between the positive metal ions and the sea of delocalised electrons
• Electrons in the outer shell are represented in a dot and cross diagram
• Giant ionic lattices conduct electricity when liquid but not when solid because in the solid state, the ions are in fixed positions and cannot move, while in the liquid state, the ions are mobile and can carry the charge
• Giant ionic lattices have high melting and boiling points because a large amount of energy is required to overcome the electrostatic bonds
• Ionic lattices dissolve in polar solvents like water
• Ionic compounds are soluble in water because water has a polar bond that can attract charged ions
• Atoms bonded by a single pair of shared electrons form a single bond
• Carbon forms 4 covalent bonds
• Oxygen forms 2 covalent bonds
• A lone pair is electrons in the outer shell that are not involved in bonding
• Atoms sharing two pairs of electrons form a double bond
• Atoms sharing three pairs of electrons form a triple bond
• Average bond enthalpy is a measure of the average energy needed to break a bond
• A dative covalent bond is a bond where both of the shared electrons are supplied by one atom
• Oxonium ions are formed when acid is added to water, resulting in H3O+
• Expansion of the octet occurs when a bonded atom has more than 8 electrons in the outer shell
• Types of covalent structure include:

  • Simple molecular lattice
  • Giant covalent lattice
• In simple molecular structures, atoms within the same molecule are held by strong covalent bonds, while different molecules are held by weak intermolecular forces
• Simple molecular structures have low melting and boiling points because a small amount of energy is enough to overcome the intermolecular forces
• Simple molecular structures do not conduct electricity because they have no free charged particles to move around
• Simple molecular structures dissolve in non-polar solvents
• Examples of giant covalent structures include diamond, graphite, and silicon dioxide (SiO2)
• Properties of giant covalent structures include:

  • High melting and boiling point
  • Non conductors of electricity, except graphite
  • Insoluble in polar and non-polar solvents
• Graphite conducts electricity due to delocalised electrons present between the layers that can move freely carrying the charge
• Giant covalent structures have high melting and boiling points because strong covalent bonds within the molecules need a lot of energy to be broken
• The structure of a diamond is a 3D tetrahedral structure of C atoms, with each C atom bonded to four others
• The shape of a molecule depends on its bonding and lone pairs
• The shape of a molecule depends on:

  • Number of electron pairs in the outer shell
  • Number of these electrons which are bonded and lone pairs
• In a molecule with 3 bonding pairs and 0 lone pairs:

  • Shape: Trigonal planar
  • Bond angle: 120
• In a molecule with 2 bonded pairs and 0 lone pairs:

  • Shape: Linear
  • Bond angle: 180°
• In a molecule with 4 bonded pairs and 0 lone pairs:

  • Shape: Tetrahedral
  • Bond angle: 109.5°
• In a molecule with 5 bonded pairs and 0 lone pairs:

  • Shape: Trigonal bipyramid
  • Bond angles: 90° and 120°
• In a molecule with 6 bonded pairs and 0 lone pairs:

  • Shape: Octahedral
  • Bond angle: 90°
• In a molecule with 3 bonded pairs and 1 lone pair:

  • Shape: Pyramidal
  • Bond angle: 107°
• In a molecule with 2 bonded pairs and 2 lone pairs:

  • Shape: Non-linear
  • Bond angle: 104.5°
• Each lone pair reduces the bond angle by 2.5°