F321 - ATOMS, BONDS & GROUPS - DEFINITTIONS

Isotopes                                    atoms of an element with different numbers of neutrons and different masses

Relative atomic mass                  average mass of an atom relative to 1/12 of the mass of a carbon-12 atom

Relative isotopic mass                mass of a particular isotope relative to 1/12 of the mass of a carbon-12 atom

Orbital                                      a region that can hold up to 2 electrons with opposite spins

1^st ionisation energy                   energy change when one mole of electrons is removed from one mole of gaseous atoms

Successive ionisation energy       energy change when one mole of electrons is removed from one mole of gaseous positively charged ions

Acid                                          proton donor (H⁺ donor)

Base                                         proton acceptor (H⁺ acceptor)

Salt                                           produced when the H⁺ of an acid is replaced by another positive ion

Oxidation                                   loss of electrons or increase in oxidation number

Reduction                                  gain of electrons or decrease in oxidation number

Disproportionation                      a reaction in which an element is simultaneously oxidised and reduced

Amount of substance                  the number of moles of substance that you have

Mole                                         unit for amount of substance

Avogadro constant, N_A                number of particles present in a mole (6.02 x 10²³ mol^-1)

Empirical formula                       simplest whole number ratio of the atoms of each element in a compound

Molecular formula                      actual number of atoms of each element in a molecule

Concentrated                             containing a large amount of solute per dm³

(say 10 mol dm^-3 or more)

Dilute                                        containing a small amount of solute per dm³

(say 2 mol dm^-3 or less)

Ionic bond                                 electrostatic attraction between oppositely charged ions

Covalent bond                            a shared pair of electrons

Metallic bond                             attraction between positive ions and delocalised electrons

Electronegativity                        ability of an atom to attract the electrons in a covalent bond

Hydrogen bond                          attraction between a lone pair and a hydrogen atom attached to O, N or F

Periodicity                                 patterns repeated across different periods (rows of the Periodic Table)