Definitions (Learn) Flashcards
Isotope
Atoms of the same element with different numbers of neutrons and different masses
Relative atomic mass
The weighted mean mass of an atom of an element compared with one–twelfth of an atom of carbon–12
1st 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
Shell
A group of atomic orbitals with the same principal quantum number, n, also known as a main energy level.
Subshell
A group of orbitals of the same type within a shell.
Atomic orbital
A region around the nucleus which can hold up to 2 electrons, with opposite spins.
Electronegativity
A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.
Hydrogen bond
A strong dipole-dipole attraction between an electron deficient hydrogen atom of -NH, -OH or HF on one molecule and a lone pair of electrons on a highly electronegative atom containing N, O or F on a different molecule.
Acid
A species that releases H+ ions in aqueous solution
Strong acid
An acid that dissociates completely in solution
Weak acid
An acid that dissociates only partially in solution
Base
A compound that neutralises an acid to form a salt
Alkali
A type of base that dissolves in water forming hydroxide ions, OH-
(Aq) ions
Salt
The product of a reaction in which the H+ ions from the acid are replaced by either ammonium or metal ions
Oxidation
A loss of electrons or an increase in oxidation number
Reduction
Gain of electrons or a decrease in the oxidation number.
Redox reaction
A reaction involving both oxidation and reduction
Homologous series
A series of organic compounds with the same functional group but with each successive member differing by CH2
Electrophile
An atom or a group of atoms which is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond.
Stereoisomers
Compounds with the same structural formula but a different arrangement of atoms in space
E/Z isomerism
A type of stereoisomerism in which different groups attached to each carbon of a C=C of a double bond may be arranged differently in space because of the restricted rotation of the C=C bond.
Cis-trans isomerism
A special type of E/Z isomerism in which there are two non-hydrogen groups and two hydrogen atoms around the C=C double bond: the cis isomer (Z isomer) has H atoms on each carbon atom on the same side; the trans isomer (E isomer) has H atoms on each carbon on different sides.
Enthalpy change of combustion
the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard condition, all reactants and products being in their standard states.
Enthalpy change of formation
the enthalpy change that takes place when one mole of a compound in its standard state is formed from its constituent elements in their standard states under standard conditions.
