First 499 words of the document:
Key Definitions for AS ChemistryAtoms and ReactionsAmber Hornsby
Key Definitions for Unit 1 Chemistry
Atoms and reactions
Acid a species that is a proton donor
Alkali type of base that dissolves in water forming hydroxide ions (OH-)
Anhydrous a substance that contains no water molecules.
Anion negatively charged ion
Atomic (proton) number the number of protons in the nucleus of an atom
Avogadro constant is the number of atoms per mole of the carbon-12 isotope (6.02x10²³)
Base a species that is a proton acceptor
Concentration the amount of solute, in mol, dissolved per 1dm³ of solution.
Cation positively charged ion
Empirical formula simplest whole-number ratio of atoms of each element present in a compound
Hydrated crystalline compound containing water molecules.
Ion charged ion (covalently bonded) or group of atoms (a molecular ion)
Isotope atoms of the same element with different numbers of neutrons.
Mass (nucleon) number number of particles (protons and neutrons) in the nucleus
Molar mass mass per mole of a substance
Molar volume volume per mole of a gas, at RTP the mV is 24dm³
Mole amount of any substance containing as many particles as there are carbon atoms in exactly 12g of
the carbon-12 isotope.
Molecule small group of atoms held together by covalent bonds.
Molecular formula the actual number of atoms of each element in a molecule
Oxidation loss of electrons or increase in oxidation number
Oxidation number measure of the number of electrons that an atom used to bond with atoms of
Oxidising agent a reagent that oxidises (takes electron from) another species
Redox reaction a reaction in which both reduction and oxidation takes place
Reducing agent a reagent that reduces (adds electron to) another species
Reduction gain of electrons or decrease in oxidation number
Relative atomic mass weighted mean mass of an atom of an element compared with one-twelfth of
the mass of an atom of carbon-12
Relative formula mass weighted mean mass of a formula unit compared with one-twelfth of the mass
of an atom of carbon-12
Relative isotopic mass mass of an atom of an isotope compared with one-twelfth of the mass of an
atom of carbon-12
Relative molecular mass weighted mean mass of a molecule compared with one twelfth of the mass
of a carbon-12 atom
Salt a chemical compound formed when a H+ ion from an acid has been replaced by a metal ion or
another positive ion.
Species any type of particle that takes place in a chemical reaction.
Standard solution solution of a known concentration
Stoichiometry - the molar relationship between the relative quantities of substances taking part on a
Water of crystallisation - water molecules that form an essential part of the crystalline structure of a