Chemistry A-Level Physical, Inorganic, and Organic Specification Flashcards

A comprehensive set of vocabulary flashcards based on the A-Level Chemistry specification, covering Physical, Inorganic, and Organic Chemistry topics including atomic structure, thermodynamics, kinetics, and analysis.

Atomic (proton) number (Z)

The number of protons in the nucleus of an atom.

Mass number (A)

The total number of protons and neutrons in the nucleus of an atom.

Isotopes

Atoms of the same element with the same number of protons but different numbers of neutrons.

Relative atomic mass ($A_r$)

The average mass of an atom of an element relative to $1/12$th the mass of an atom of carbon-12 ($^{12}C$).

Relative molecular mass ($M_r$)

The average mass of a molecule relative to $1/12$th the mass of an atom of carbon-12 ($^{12}C$).

Avogadro constant

The number of particles in one mole of a substance.

Mole

The amount of substance that contains the same number of particles as there are atoms in exactly $12\,g$ of carbon-12.

Concentration

The amount of a substance in a given volume of solution, measured in $mol\,dm^{-3}$.

Ideal gas equation

$pV = nRT$, where $p$ is pressure in Pa, $V$ is volume in $m^3$, $n$ is the number of moles, $R$ is the gas constant, and $T$ is temperature in K.

Empirical formula

The simplest whole number ratio of atoms of each element in a compound.

Molecular formula

The actual number of atoms of each element in a compound.

Percentage atom economy

$$\frac{M_r \text{ of desired product}}{\text{sum of molecular masses of all reactants}} \times 100$$

Ionic bonding

The electrostatic attraction between oppositely charged ions in a lattice.

Single covalent bond

A chemical bond that contains a shared pair of electrons.

Co-ordinate (dative covalent) bond

A shared pair of electrons where both electrons are supplied by one of the atoms.

Metallic bonding

The attraction between delocalised electrons and positive ions arranged in a lattice.

Electronegativity

The power of an atom to attract the pair of electrons in a covalent bond.

Enthalpy change ($\Delta H$)

The heat energy change measured under conditions of constant pressure.

Standard enthalpy of combustion ($\Delta_c H^{\theta}$)

The enthalpy change when one mole of a substance is burned completely in oxygen under standard conditions of $100\,kPa$ and a stated temperature.

Standard enthalpy of formation ($\Delta_f H^{\theta}$)

The enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions.

Mean bond enthalpy

The average energy required to break a specific type of bond in a range of different gaseous molecules.

Activation energy ($E_a$)

The minimum energy required for collisions between particles to result in a chemical reaction.

Catalyst

A substance that increases the rate of a chemical reaction by providing an alternative route of lower activation energy, without being changed in chemical composition or amount.

Le Chatelier’s principle

A principle used to predict that the position of equilibrium will move to counteract changes in temperature, pressure, or concentration in a homogeneous reaction.

Oxidation

The process of electron loss.

Reduction

The process of electron gain.

Oxidising agent

A species that accepts electrons.

Reducing agent

A species that donates electrons.

Lattice enthalpy

The enthalpy change described as either lattice dissociation or lattice formation for an ionic compound.

Enthalpy of hydration

The enthalpy change when one mole of gaseous ions is dissolved in water to form an aqueous solution.

Entropy change ($\Delta S$)

A measure of the change in disorder of a system; for a reaction to be feasible, the Gibbs free-energy change ($\Delta G$) must be zero or negative.

Gibbs free-energy change equation

$$\Delta G = \Delta H - T\Delta S$$

Order of reaction

The power to which the concentration of a reactant is raised in the rate equation, typically limited to values of 0, 1, or 2.

Arrhenius equation

$k = Ae^{-E_a/RT}$, where $k$ is the rate constant, $A$ is the Arrhenius constant, $E_a$ is activation energy, $R$ is the gas constant, and $T$ is temperature in K.

Standard electrode potential ($E^{\theta}$)

The potential of an electrode measured under standard conditions of $298\,K$, $100\,kPa$, and $1.00\,mol\,dm^{-3}$ solution of ions.

Brønsted-Lowry acid

A species that acts as a proton donor.

Brønsted-Lowry base

A species that acts as a proton acceptor.

$$pH$$

A logarithmic scale for hydrogen ion concentration defined as $pH = -\log_{10}[H^+]$.

Ionic product of water ($K_w$)

The equilibrium constant for the self-ionization of water, defined as $K_w = [H^+][OH^-]$.

Buffer solution

A solution that maintains an approximately constant $pH$ despite dilution or the addition of small amounts of acid or base.

Transition metal

An element that forms at least one stable ion with an incomplete d sub-level, characterized by complex formation, coloured ions, and variable oxidation states.

Ligand

A molecule or ion that forms a co-ordinate bond with a transition metal by donating a pair of electrons.

Complex

A central metal atom or ion surrounded by ligands.

Co-ordination number

The number of co-ordinate bonds to the central metal atom or ion.

Chelate effect

The observation that multidentate and bidentate ligands replace monodentate ligands from complexes due to a positive entropy change.

Heterogeneous catalyst

A catalyst that exists in a different phase from the reactants, where the reaction occurs at active sites on the surface.

Homogeneous catalyst

A catalyst that exists in the same phase as the reactants and proceeds through an intermediate species.

Autocatalysis

A process where a reaction product (such as $Mn^{2+}$ in the reaction between $C_2O_4^{2-}$ and $MnO_4^-$) acts as a catalyst for the reaction.

Structural isomerism

Compounds with the same molecular formula but different structural formulas.

Stereoisomerism

Compounds with the same structural formula but with atoms arranged differently in space (includes E–Z and optical isomerism).

Thermal cracking

A process taking place at high pressure and high temperature that produces a high percentage of alkenes.

Catalytic cracking

A process taking place at slight pressure and high temperature in the presence of a zeolite catalyst to produce motor fuels and aromatic hydrocarbons.

Biofuel

A fuel, such as ethanol from fermentation, which is derived from renewable biological resources.

Nucleophile

An electron pair donor.

Electrophile

An electron pair acceptor.

Optical isomerism

A form of stereoisomerism occurring in molecules with a chiral (asymmetric) carbon centre, resulting in non-superimposable mirror images called enantiomers.

Peptide link

The linkage that joins amino acids together in a protein sequence.

Nucleotide

A unit consisting of a phosphate ion bonded to 2-deoxyribose, which is bonded to one of four nitrogenous bases.

Chemical shift ($\delta$)

A measure of the molecular environment of atoms (such as $^{13}C$ or $^1H$) recorded in NMR spectroscopy relative to a standard like tetramethylsilane (TMS).