Chapter 6

• 2.6.1 - 3 point of electron-pair repulsion theory.


  1. The electron pairs determinds the shape of molecule or ion

  2. Electron repeal each other —> aranged as far apart as possible

  3. Different number of electron pair result in different shapes
• 2.6.1 - what does a solid line present?

  A bond in the plane of the paper
• 2.6.1 - what does a solid wedge represent?

  Comes out of the paper
• 2.6.1 - what does a dotted wedge represent?

  Goes into the plane of the paper
• 2.6.1 - how does bonded pair and lone pair electrons work?

  Bonded-pair/bonded-pair < bonded-pair/lone pair < lone-pair/lone-pair
• 2.6.1 - all about tetrahedral shape


  - bonded pairs of 4

  - lone pairs 0

  - angle 109.2

  - draw or describing the shape
• 2.6.1 - all about pyramidal shape


  - bonded pairs of 3

  - lone pair of 1

  - angles 107

  - draw or describing the shape
• 2.6.1 - all about non-linear shape


  - bonded pairs 2

  - lone pairs of 2

  - angles 104.2

  - draw or describing the shape
• 2.6.1 - how is angle effected.


  As a lone pair of electron is added the angle decreases by 2.5
• 2.6.1 - all about linear shape


  - bonded pairs of 2

  - angles 180

  - draw or describing the shape
• 2.6.1 - all about triangle planer shape


  - bonded pairs of 3

  - angles 120

  - draw or describing the shape
• 2.6.1 - all about octahedral


  - bonded pairs of 6

  - angles 90

  - draw or describing the shape
• 2.6.1 - electrons in ion and some examples


  Electron-repulsion theory can also be used for ions

  - e.g. NH+4 and CO3-2 form triangular planer shape

  - e.g. SO4-2 forms tetrahedral shape
• 2.6.2 - what is electronegativity


  It is the ability of an atom to gain electron
• 2.6.2 - how can electronegativity be measured?


  By Pauling scale

  - the learner the Pauling scale —> the higher the electronegativity of the atom or element
• 2.6.2 - so are they covalent or ionic?


  One of the element would be more desperate to gain an electron then the other elements which causes the covalent changes to either polar covalent bond or ionic bond.

  A difference of more than 1.8 in electronegativity of two elements or atoms will make the compound an ionic one, no difference would be pure covalent and lower than 1.8 would be polar covalent bond
• 2.6.2 - what are polar bonds?


  Polar covalent bond - have slight positive charge and slight negative charge, delta means small, these charges are shown by delta.
• 2.6.2 - difference between a dipole and premanent dipole


  Dipole - The separation of opposite charges

  Permanent dipole - a dipole in covalent bond does not change
• 2.6.2 - what are Non-polar bonds?


  In non-polar molecule the bonded pairs shared equally between the bonded atoms.

  • bonded atoms are the same

  • bonded atoms are the same or similar electronegativity. These are pure covalent bonds
• 2.6.3 - what are intermolecular forces


  They are weak interaction between dipoles of different molecules
• 2.6.3 - what are the three quote of intermolecular forces


  - induce dipole-dipole interaction (London force)

  - permanent dipole-dipole interaction

  - hydrogen bond
• 2.6.3 - what are induced dipole-dipole interaction and explain it.

  - movement of electrons causes change in dipole —> instantaneous dipole will exist - with shifting positions

  - this instantaneous dipole induces dipole on the neighbouring Molecules

  - induce dipole further induces further on other neighbouring molecules, attracting one another - temporary
• 2.6.3.- what are permanent dipole-dipole interactions

  permanent dipole-dipole act between the permanent dipole in different polar molecules.
• 2.6.3 - what what forces would non-polar molecule have


  Only London forces between molecules and covalent bond within the molecule
• 2.6.3 - what forces would a polar molecule have


  Permanent dipole-dipole interaction, London forces and hydrogen bonds
• 2.6.3 - what are simple molecule substance


  Are made of simple molecules.

  Eg h2, 02, h20

  In solid state, simple molecule form a regular strcuture called simple molecular lattic.
• 2.6.3 melting and boiling point of simple molecule substance


  - low melting and boiling points

  - when molecule lattice is broken apart only the intermolecular forces are broken the covalent bond doesn't break as it is strong
• 2.6.4 - what is hydrogen bonding


  Is a special type of permanent dipole-dipole interaction found between molecules containing :

  • electron negative atom with lone pair of electron eg O, N, F

  • A hydrogen atom attract to a n electronegative atom eg H-O, H-N
• 2.6.4 - what structure and bond does hydrogen bonding form

  Hydrogen bonds form linear angle 180
• 2.6.4 - how does hydrogen bonding works

  Hydrogen bond acts between a lone pair of electrons on an electronegative atom in a molecule and a hydrogen atom in a different molecule.
• 2.6.4 - one anomalous property of water which involves density


  Solid (ice) is less dense than the liquid (water

  • hydrogen holds h20 molecule apart

  • Molecule further apart in solid then water
• 2.6.4 - what is the boiling and melting boing of hydrogen bonds


  High melting and boiling point

  • compare to other simple covalent compound

  • Because it has the hydrogen bond and London bond
• 2.6.4 - what is meant by surface tension and viciously of water


  Relatively high surface tension and viscosity

  • this is mainly due to hydrogen bond

  • This result in droplets that are 'not wet' and allow in insect to walk on pond surface.
• 2.6.3 - solubility of non-polar molecule substance


  - non-polar substance can dissolves in non-polar solvent because intermolecular forces forms between the molecule and solvent breaking the intermolecular forces between the molecule themselves

  - non-polar substance can't dissolve in polar substance because the formation of intermolecular force between the molecule and polar solvent doesn't happen
• 2.6.3 - solubility of polar simple molecule substance

  • polar substance dissolves in polar solvent

  • Solubility depends on the strength of the dipole and can be hard to predict

  - polar