Chemistry OCR A

• Anhydrous


  Contains no waters of crystallisation
• First ionisation energy


  The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions.
• Factors affecting ionisation energy?

  S - atomic shielding increases reducing the attraction between the nucleus and the outer electrons.

  C - nuclear charge more protons in the nucleus - the greater the attraction.

  AR - atomic radius increase the distance between _______ decreases the nuclear attraction (large effect).
• Trend in first ionisation down a group.

  S - increase

  C - ignore

  AR - increases
• Trend in first ionisation across a period.

  S - similar shielding

  C - increases

  AR - decreases
• Oxidation def. and no.

  loss of electrons

  oxidation number increases
• Reduction def. and no.

  gain of electrons

  oxidation numbers decrease
• Trend in boiling point down the halogens.

  Increases

  more electrons

  stronger London forces

  more energy required to break IMF
• Trend in reactivity of halogens down the group.

  Decreases

  S - increase

  C - ignore

  AR - increases
• Base


  a compound that neutralises an acid to form a salt.
• hydrated


  a crystallised compound containing water molecules.
• isotope

  atoms of the same element with different number of neutrons and different mass number. Isotopes of the same element have the same chemical properties but may have small differences in physical properties.
• Acid

  In water an acid releases Hydrogen ions H+ into a solution.
• Alkali

  an alkali is a type of base that dissolves in water forming hydroxide ions OH-
• Relative atomic mass (Ar)


  Weighted mean mass compared with 1/12th mass of a carbon-12 atom.
• Relative isotopic mass

  mass of the isotope compared with 1/12th mass of a carbon-12 atom.
• A salt


  a salt is the product of a reaction in which the H+ ions from the acid are replaced by the metal or ammonium ions.
• strong acid

  A strong acid releases all of its hydrogen as ions in solution and completely disassociates.
• Water of crystallisation

  Water molecules that are bonded into a crystalline structure of a compound.
• weak acid

  a weak acid only releases a small number of its hydrogen as ions in solution and partially disassociates.
• P-orbitals

  Shaped like a dumb-bell.
• S-orbital

  Spherical

  the greater the shell orbital, the larger the radius of the s orbital.
• The Aufbau Principle

  The 4s sub-shell has lower energy than the 3p orbital so is occupied first.
• Hund’s rule


  single electrons occupy all empty orbitals within a sub-shell before they start to form pairs.
• The 4s sub-shell


  Fills first and empties first.
• Exceptions to 4s filling first.

  Chromium and copper.

  They gain one 4s electron and the remaining join the 3d sub-shell.
• Nobel gases

  They have a full principle energy level.

  They don’t want to bond with other elements.
• What is an ionic bonding?

  an ionic bond is the electrostatic attraction between oppositely charged ions.
• ammonium

  NH4+
• hydroxide

  OH-
• Sulfate

  SO4 2-
• Nitrate

  NO3 -
• Carbonate

  CO3 2-
• What is an ionic bond?

  The electrostatic force of attraction between oppositely charged ions.
• Melting and boiling point of ionic compounds?

  high melting and boiling points due to the very strong bonds between the ions.
• Are ionic compounds a solid, liquid or gas at room temperature.

  Solids.
• Solubility of ionic lattices.


  They can dissolve in polar solvents.

  The polar molecules breakdown the lattice by surrounding each ion to form a solution.
• Ionic compounds conducting electricity.

  Only if the ions can move.

  when solid - ions are fixed.

  when molten - ions can move.

  when dissolved - ions can move
• Definition of a covalent bond?

  A shared pair of electrons.
• What is a dative covalent bond?

  A shared pair of electrons which have been provided by one of the bonding atoms only.