3.1.3 Bonding

Cards (55)

  • Covalent bonding: When two atoms share pairs of electrons
  • A dative covalent bond forms when the shared pair of electrons in the covalent bond comes from only one of the bonding atoms.
  • Metallic bonding: the electrostatic force of attraction between positive metal ions and delocalised electrons
  • What are the 3 main factors affecting the strength of metallic bonding?
    1. Nuclear Charge
    2. Number of Delocalised Electrons per atom
    3. Size of Ion
  • What structure do ionic structures take? Giant Ionic Lattice
  • What are the properties of ionic compounds?
    • They are usually crystalline solids.
    • They have high melting points and boiling points.
    • They are usually soluble in water
    • They conduct electricity when dissolved in water or when melted
  • Explain 3 key properties of metals
    • High melting points due to strong metallic bonds in giant metallic structures, these are hard to break
    • Good conductors of electricity because delocalised electrons can move through the structure and carry a charge
    • Malleable because layers of ions can slide over each other, held together by electrostatic forces
  • Describe properties of simple molecules
    • Low boiling / melting points  - due to weak intermolecular forces between molecules
    • Poor conductivity because there aren't any ions + electrons are localised
  • Linear:
    • b.p = 2
    • l.p = 0
    • bond angle = 180
    • example = CO2 BeF2
  • Trigonal Planar
    • b.p = 3
    • l.p = 0
    • bond angle = 120
    • example = BF3 , AlCl3
  • Tetrahedrall:
    • b.p = 0
    • b.p = 4
    • bond angle = 109.5 
  • Trigonal Bipyramidal:
    • b.p = 5
    • l.p = 0
    • b.a = 90 and 120
  • Trigonal Pyramida:
    b.p = 3
    l.p = 1
    b.a = 107
  • Bent
    • b.p = 2
    • l.p = 2
    • b.a = 104.5
    • examples = H20, SCl2
  • What shape is formed from 4 bp and 1 lp? see-saw
  • What shape is formed from 3 b.p and 2 l.p? T shape
  • What shape is formed from 3 l.p and 2 b.p? Linear
  • What shape is made from 4 bond pairs and 2 lone pairs? Square Planar
  • Electronegativity: the power of an atom to attract bonded electrons in a covalent bond towards itself
  • FONCI are the most electronegative atoms
  • Electronegativity is measured on the Pauling scale, ranging from 0 to 4
  • Electronegativity will increase across a period as the number of protons increases but there is similar shielding.
  • Electronegativity will decrease down a group because the distance between the nucleus and bonded electrons increase and the shielding of the inner shell electrons increases.
  • Dipole moment: The overall effect of polarity of the bonds in a molecule
  • Describe van der Waals’ forces of attraction:
    • Temporary dipoles are created by the random movement of electrons
    • → induces dipole in neighbouring molecule
    • temporary induced dipole-dipole attraction aka van der Waals forces of attraction
  • What factors lead to stronger Van Der Waals forces?
    • More electrons
    • Bigger surface area
  • The boiling point of halogens down group 7 increases because there are more electrons in bigger molecules .
  • Long chain alkanes have a higher b.p than spherical shaped alkanes because ...

    There is a larger surface area of contact between chained molecules than there is spherical molecules.
  • Describe permanent dipole-dipole forces:
    • Electrostatic forces between polar molecules
    • Stronger than Van der Waals so compounds have higher boiling point
  • What is hydrogen bonding? The strongest type of intermolecular force that forms between Hydrogen and F, O, N. The lone pair on these atoms attract a hydrogen atom on another molecule.
  • 3 types of intermolecular forces:
    1. Van Der Waals
    2. Dipole-Dipole
    3. Hydrogen Bonds
  • What are the 4 types of crystal structures?
    1. Ionic
    2. Metallic
    3. Simple Molecular
    4. Giant Covalent
  • Describe the properties of simple molecular compounds
    1. low melting point because of weak intermolecular forces
    2. poor solubility in water
    3. poor conducitivity of electricity in solid/when molten as there are no ions / electrons are localised
    4. generally mostly gases and liquids
  • State 5 properties of metals
    • high mp/bp due to strong attraction between +ve ions and sea of delocalised electrons
    • insoluble
    • good conductors of electricity
    • shiny
    • malleable, as layers of ions can slide over each other
  • Solid: 
    • Arrangement: Tightly packed in a regular arrangement
    • Movement: Vibrate in fixed positions
  • Liquid:
    • Arrangement: Tightly packed in a random arrangement
    • Movement: Particles move freely and have more energy than in a solid
  • Gases:
    1. Arrangement: Spaced out and in a random arrangement
    2. Movement: Particles move freely and have lots of energy
  • Graphite is soft because the structure is in planes/layers and weak bonds between planes mean they can slide
  • Electronegativity: The power of an atom or nucleus to withdraw or attract a pair of electrons in a covalent bond
  • The melting point of carbon is high because:
    • the macromolecular structure is giant.
    • Covalent bonds in the structure are strong
    • and require lots of energy to break