Module 2.2.2- Bonding and structure

    Cards (42)

    • Ionic bonding
      The electrostatic attraction between oppositely charged ions
    • MgCl2 dot and cross diagram
    • Giant ionic lattice
      A 3D structure of oppositely charged ions, bonded together by strong ionic bonds
    • Properties of giant ionic structures: high melting and boiling point

      High temperatures are needed to provide the large quantity of energy needed to overcome the strong electrostatic attraction between the ionsmelting point increases with greater ionic charges
    • Properties of giant ionic structures: solubility
      Most ionic compounds dissolve in polar solvents. Polar water molecules break down the lattice and surround each ion in solution.Solubility requires 2 main processes:- ionic lattice must break down- water molecules must attract and surround the ionssolubility decreases as ionic charge increases
    • Properties of giant ionic structures: electrical conductivity
      Not conduct when solid since ions are in a fixed position with no mobile charge carriersConduct when liquid since ions are free to move as mobile charge carriers
    • Covalent bonding
      The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
    • Difference in attraction between ionic and covalent
      Ionic- attracts in all dimensions
      Covalent- localised
    • Single covalent bonds dot and cross diagram
    • Multiple covalent bonds dot and cross diagram
    • Dative covalent bond
      A shared pair of electrons which has been provided by one of the bonding atoms only
    • Average bond enthalpy
      The average enthalpy change that takes place when breaking by homolytic fission 1 mole of a given type of bond in the molecules of a gaseous species.Measurement of covalent bond strength
    • Electron pair repulsion
      electron pairs repel one another so they are arranged as far as possible
    • Lone pair repulsion in comparison to bonding pair

      Lone pairs repel more than bonding pairs
    • explaining the shape of a molecule

      There are X bonded pairs and X lone pairs
      Electron pairs repel one another so they are arranged as far apart as possible
      Lone pairs repel more than bonding pairs(decreasing bond angle)
    • Trigonal pyramidal
      3 bonded pairs
      1 lone pair
      107
      e.g. NH3
    • Tetrahedral shape

      4 bonded pairs
      symmetrical
      0 lone pairs
      109.5
      e.g. CH4
    • Non-linear
      2 bonded pairs
      2 lone pairs
      104.5
      e.g. H2O
    • Linear
      2 bonding regions
      0 lone regions
      180
      4 bonded pairs count as 2 bonding regions due to the double bond e.g. CO2
    • Trigonal Planar

      3 bonds
      0 lone pairs
      120
    • Octahedral
      6 bonds
      0 lone pairs
      90
    • Shape of ions NH4+
      Tetrahedral structure
      109.5
    • Shape of ions CO3^2-
      Trigonal Planar 120
    • Shape of ions NO3^2-
      Trigonal Planar 120
    • Shape of SO4^2-
      Tetrahedral 109.5
    • Electronegativity
      electronegativity as the ability of an atom to attract the bonding electrons in a covalent bond
    • Non-polar bond

      The bonded electron pair is shared equally between the bonded atomsBonded atoms are the same or have similar electronegativity e.g. C-H bonds
    • Pure covalent bond
      A covalent bond with equal sharing of electrons between atoms.
    • Polar covalent bond
      A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.
    • Permanent dipole
      A small charge difference across a bond resulting from a difference in electronegativities of the bonded atoms.
    • Intermolecular forces
      Weak interactions between dipoles of different molecules
    • 3 types of intermolecular forces

      London forces
      Permanent dipole-dipole
      Hydrogen bonding
    • Strength of London forces
      -The more electrons in each molecule: the larger the instantaneous and induced dipoles, the greater the induced dipole-dipole interactions, the stronger the attractive forces between molecules.-Larger numbers of electrons mean larger induced dipoles. More energy is then needed to overcome the intermolecular forces, increasing the boiling point.
    • Simple molecular substance/lattice
      substance made up of simple molecules held together by covalent bonds and has weak intermolecular forces between these molecules
    • Properties of simple molecular lattice- low melting and boiling point

      due to the weak intermolecular forces between the molecules, which break under low temperaturescovalent bonds do not break!
    • Properties of simple molecular lattice- solubility of non polar substances
      non-polar simple molecular substances tend to be soluble in non-polar solvents
      simple molecular substances tend to be insoluble in polar solvents
    • Properties of simple molecular lattice- solubility of polar substances
      polar covalent substances may dissolve in polar solventssolubility depends on the strength of the dipole
    • Properties of simple molecular lattice- electrical conductivity
      no mobile charged carriers in simple molecular structurestherefore they are non-conductors of electricity
    • Hydrogen bonds with...

      Nitrogen
      Oxygen
      Fluorine
    • Why is ice less dense than liquid water?

      hydrogen bonds holds water molecules apart in an open lattice structure (fixed)the water molecules in ice are further apart than in liquid water
    See similar decks