Definitions

• Mass number

  Total number of protons and neutrons.
• Atomic number

  Numbers of protons in the nucleus and number of electrons in shells.
• Negative Ions

  More electrons than protons.
• Positive ions

  More protons than electrons.
• Relative isotopic mass

  mass of an atom of an isotope of an element on a scale where an atom of carbon12 is 12.
• Relative atomic mass

  average mass of an atom of an element on a scale where an atom of carbon12 is 12.
• Relative molecular mass

  average mass of a molecule on a scale where an atom of carbon12 is 12.
• First ionisation energy

  the energy needed too remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.
• Second ionisation energy


  the energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.
• Number of particles=

  Number of moles x Avagadros constant (6.02 x 10^23)
• Number of moles=

  Mass / Mr
• Number of moles=

  Concentration (moldm^-3) x Volume (dm^3)
• Methyl orange indicator

  yellow in acid, red in alkali. Commonly used in titrations.
• Phenolphthalein indicator


  pink in alkali, colourless in acid. Commonly used in titrations.
• Avogadros constant


  the number of atoms in 12g of carbon12 (6.02 x 10^23)
• Ideal gas equation


  Pv= nRT
• Empirical formula

  simplest whole number ratio of atoms of each element in a compound.
• Molecular formula

  gives the actual numbers of each element in a molecule.
• Percentage yield

  how much product was actually made compared with the amount of product that was expected
• theoretical yield

  the maximum mass of product expected in a reaction.
• actual yield

  the mass of product that is actually obtained in a reaction.
• Atom economy

  measure of the efficiency of a chemical reaction. The proportional mass of reactants that actually become part of the desired product in a balanced chemical equation.

  
• Ionic bonding

  Ions (metal and non metal) are held together by electrostatic forces of attraction due to the transferring of electrons. Eg: Sodium chloride.

  
• Mass spectrometer

  An instrument used to accurately determine the relative atomic mass. Separates atoms or molecules (gaseous positive ions) according to their charge and mass.
• Orbital

  Region in space where one is likely to find up to two electrons with opposite spin.
• Covalent Bonding

  holds molecules together by sharing electrons between non-metals. Eg: I2, Graphite, Diamond.

  
• Dative Covalent Bonding

  Where both electrons are provided by one atom for a covalent bond.

  
• Linear molecule


  2 bonds 180 degree angles 2D e.g: CO2

  
• Trigonal planar molecule


  3 bonds 120 degree angles 2D e.g: BF3

  
• Tetrahedral molecule


  4 bonds 109.5 degree angles 3D e.g: CH4

  
• Trigonal bipyramid molecule


  5 bonds 120 degree and 90 degree angles 3D e.g.: PCl5

  
• Octahedral molecule


  6 bonds 90 degree angles 3D e.g.: SF6

  
• Lone pairs

  Cause a repulsion of 2.5 degrees.
• Charge Clouds

  What bonding pairs and lone pairs exist as in a molecule.
• Largest repulsion angle in a molecule

  lone pair - lone pair
• 2nd largest repulsion angle in a molecule

  lone pair - bonding pair
• Smallest repulsion angle in a molecule

  bonding pair - bonding pair
• Electronegativity

  An atoms ability to attract the electron pair in a covalent bond
• Polar

  caused by the difference in electronegativity in a covalent bond, where the electrons are pulled towards the more electronegative atom creating a dipole.

  
• Dipole

  difference in charge between atoms created by a shift in electron density within the bond.