Bonding

• Metallic bonding brain download.

  Is:

  • Between metal and metal
  • Delocalised electrons move through the sea of positively charged metal ions
  • Forms giant metallic lattice
  • Physical properties are- Good conductors of heat and electricity, most are Silver, Strong, Hard, Dense, has HIgh Melting and Boiling points, Ductile, Malleable, Sonorous and Lustrous.
• Ionic bonding brain download.


  Is:

  • Between metal and non-metal
  • Electrons are transferred from metal to non-metal to form oppositely charged ions
  • Forms giant ionic lattice
  • Physical properties are- High melting and Boiling points, most are solids at room temperature, conducts electricity when moten/dissolved, soluble in water, brittle and shatter easily
• Brain download on covalent bonding.


  Is:

  • between non-metal and non-metal
  • Pairs of electrons is shared
  • Double bond forms in double bond forms in CO2 and O2 and alkenes, triple bonds form in N2
  • Can form small molecules (like H2) and macromolecules (like diamond/fullerene/graphene/graphite/silicon dioxide)
  • Physical properties are High melting and boiling points (depends on substance as graphite is soft, diamond is hard)
  • The larger the molecule, the more the intermolecular forces are in the molecule
• What is the empirical formula?

  Simplest ratio of atoms of each element in a compound.
• What is a polyatomic ion?


  An ion made from more than one atom.
• What is the formula for an ammonium ion?

  $NH_4^+$
• What is the formula for a nitrite ion?


  $NO_2^-$
• What is the formula for a nitrate ion?


  $NO_3^-$
• What is the formula for a sulfite ion?

  $SO_3^-2$
• What is the formula for a sulfate ion?

  $SO_4^-2$
• What is the formula for a hydroxide ion?

  $OH^-$
• What is the formula for a phosphate ion?

  $PO_4 ^-3$
• What is the formula for a carbonate ion?

  $CO_3^-2$
• What is the formula for a chlorate ion?

  $ClO_3^-$
• What is the formula for a hydrogen carbonate?

  $HCO_3^-$
• What is the formula for a permanganate ion?

  $MnO_4^-$
• What is the formula for an ethanoate ion?

  $-CH_3COO^-$
• What is the formula for a hydronium ion?

  $H_3O^+$
• What is the formula for a chromate ion?

  $CrO_4^-2$
• What is the formula for a dichromate ion?

  $Cr_2O_7^-2$
• What is an electron deficient atom?

  An atom that does not have a full outer main shell of electrons
• What is a lone pair?

  An atom with a spare pair of electrons that is not being used in a present bond
• What is a coordinate bond?

  A covalent bond where a shared pair of electrons are both provided by one atom
• What is electronegativity?

  A measure of the tendency of an atom to attract a bonding pair of electrons, measured using the Pauling scale
• What is the highest electronegativity an element can have?

  4.0 which is fluorine.
• What is the smallest electronegativity an element can have?

  0.7 which are caesium and francium.
• When can two atoms have the same electronegativity and why?

  When they are diatomic as this means that the pull on the electron pair is equal so there is an even cloud of electrons.
• What happens when an atom has more electronegativity than the other e.g. HF?

  Fluorine would attract more electrons as it has a higher electronegativity, so will have a higher cloud of electrons and hydrogen will be smaller with less electrons. The fluorine atom becomes delta negative and the hydrogen will become delta positive
• What is a polar bond?

  A covalent bond where there is an unequal distribution of electrons which causes an uneven balance of charge.
• How can an induced dipole be formed due to electronegativity? e.g. AB

  If atom A is more electronegative then it will pull more electrons towards it and this causes B to become delta positive and A to become delta negative, this means that a nearby molecule will become attracted to the delta charges, and due to the movement of electrons, this can cause the nearby atom to become delta negative if it is near atom B of AB.
• What are diatomic atoms considered as?

  Pure covalent bonds- electrons are held exactly halfway between both atoms.
• What is the trend in electronegativity?

  Increases up a group and across a period.
• Why does electronegativity increase up a group?

  Elements have less shells up a group, meaning less shielding so the nucleus is closer to the bonding pair and this increases attraction between the nucleus and bonding pair.
• Why does electronegativity increase across a period?

  Nuclear charge increases so atomic radius decreases, thus nucleus is closer to the bonding pair and becomes more strongly attracted to it.
• Where on the periodic table is most electronegative?

  Top right corner- exclude Noble Gases.
• What is the shape of a molecule depend on?

  The number of bonding pairs of electrons and lone pairs that are around the central atom.
• What are orbitals?

  Regions around the nucleus where electrons are likely to be found.
• How is the shape of a simple covalent molecule deduced?

  • Each pair of electrons around an atom will repel all other electron pairs as like-charges repel
  • Pairs of electrons will therefore take up positions as far apart as possible to minimise repulsion
  • Known as the electron pair repulsion theory
  • (Lewis structure?)
• What determines the shape of a molecule?

  The number of electrons it has.
• What is the first step to determining the shape of a molecule?

  Counting the total number of valence electrons by drawing a dot and cross diagram.