Definitions

• what is relative isotopic mass?

  mass of an isotope relative to 1/12 th of the mass of an atom of carbon-12
• what is the relative atomic mass?

  The weighted mean mass of an atom relative to 1/12 th of the mass of an atom of carbon-12
• What is the weighted mean mass?

  The mean mass taking into account the relative abundancies of the isotopes
• what is an isotope?

  atoms of the same elements with different number and neutrons and different masses
• what is the avogadro constant?

  number of particles in each mole of carbon-12
• molar mass

  mass in grams in each mole of the substance
• Mole

  one mole is the amount of a substance that contains 6.02 x 10²³ atoms
• amount of a substance (n)

  quantity to count the number of particles In a substance
• Molecular formula

  number of atoms in each elements in a molecule
• empirical formula

  simplest whole number ratio of atoms of each element In a compound
• relative molecular mass

  compares the mass of a molecule with the mass of an atom of carbon-12
• relative formula mass

  compares the mass of a formula unit with the mass of an atom of carbon-12
• analysis

  investigating the chemical composition of a substance
• hydrated

  water molecules are part of their crystalline structure
• water of crystallisation

  when compound forms crystals that have water as part of their structure

  • compounds that contain water of crystallisation are hydrated
• anhydrous

  doesn’t contain water of crystallisation

  • bonds holding the water within crystal is broken and driven off
• standard solution


  solution of known concentration
• molar gas volume

  volume per mole of gas molecules at a stated temperature and pressure
• stoichiometry

  ratio of balanced equations
• atom economy

  measure of how well atoms have been utilised in a chemical reaction
• strong acid

  acid that completely dissociates in aqueous solution to release H+ ions
• weak acid

  acid that partially dissociates in aqueous solution to release H+ ions
• atomic orbital

  region around the nucleus that can hold up to two electrons with opposite spins
• ionic bonding

  electrostatic attraction between positive and negative ions

  (oppositely charged ions)
• covalent bonding

  electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
• dative covalent bond

  covalent bond where the shared pair of electrons has been supplied by only one of the bonding atoms
• average bond enthalpy

  measure of the covalent bond strength
• electronegativity

  attraction of the bonded atom for the pair of electrons in a covalent bond
• non polar bond


  bonded electron pair is shared equally between the bonded atoms
• polar bond


  bonded electron pair is shared unequally between the bonded atoms
• permanent dipole

  dipole in the polar covalent bond
• intermolecular forces

  weak interaction between dipoles of different molecules
• simple molecular substances

  made of of small units containing a definite number of atoms with definite molecular formula
• first ionisation energy


  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
• Disproportionation

  simultaneous oxidation and reduction of the same element in a REDOX reaction
• metallic bonding

  Strong electrostatic attraction between cations and delocalised electrons
• enthalpy


  measure of the heat energy in a chemical system
• activation energy

  minimum energy required for a reaction to take place
• standard enthalpy change of formation

  enthalpy change that takes place when one mole of a compound is formed from its elements under. standard conditions

  (all reactants and products in their standard states)
• standard enthalpy change of fcombution

  enthalpy change that takes place when one mole of a substance completely reacts with oxygen under standard conditions

  (all reactants and products in their standard states)