All definitions for OCR a A-level chemistry

Atomic number

Number of protons or electrons in an element

Mass number

Number of protons plus neutrons

Isotopes

Atoms of the same elements that have different number of neutrons

Relative atomic mass

The average mass of an atom of an element relative to 1/12 of the mass of a carbon 12 atom

M/Z

Mass charge ratio

Acid

Releases H+ ions in solution

Alkali

Releases OH- ions into solution

Strong acid/alkali

Fully dissociated in solution

Weak acid/alkalife

Partially dissociated in solution

Neutralisation

Reaction of H+ and OH- ions to form H²O

Standard solution

A solution of accurate concentration

Oxidising agent

Electron acceptor

Reducing agent

Electron donor

Orbital

A region that can hold two electrons of opposite spins

Covalent bond

Electrostatic attraction that occurs due to the sharing of two electrons between two non-metal atoms

Ionic bond

Electrostatic attraction that occurs due to the electron transfer from a metal to a nonmetal forming positive and negative ions

Metallic bonds

Electric static attraction that occurs when a positive metal iron is surrounded by a sea of delocalised electrons

Electronegativity

The ability of an atom to attract electrons towards itself in a covalent bond

Ionisation energy

The energy required to remove one mole of electrons from gaseous atoms to form one mole of gaseous ions

Disproportionation

Simultaneous oxidation and reduction of a species

Activation energy

Minimum energy required for a reaction to occur

Enthalpy of combustion

And we change when one mole of a substance is completely burned in excess oxygen

Enthalpy of formation

Enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions

Enthalpy of neutralisation

Enthalpy change when one mole of water is formed in an acid-base neutralisation reaction

Standard conditions

100kPa & 298K & 1 moldm³ H+ ions

Standard states

Physical states understandard conditions

Equilibrium

The rate of the Fords and backwards reactions are equal and the concentrations of reactants and products are constant

Homologous series

Family of compounds with the same general formula, the same empirical formula, similar reactivity, and shows a trend in physical properties

Functional group

The reactive part of the molecule

Alkyl group

CnH2n+1

Aliphatic

A compound containing carbon and hydrogen in straight chains, branched compounds, or cyclic compounds (but not aromatic)

Alicyclic

A cyclic aliphatic compound (not aromatic)

Aromatic

A compound containing benzene

Saturated

Contains single C-C bonds only

Unsaturated

Contains double or triple bonds

Structural isomers

Two molecules with the same molecular formula but different structural formula

Homolytic fission

Splitting of a bond to form two radicals, each gets one electron

Heterolytic fission

Splitting of a bond to form two opposently charged ions, one gets both electrons

Sigma Bond

Overlap of two s-orbitals

Pi Bond

Overlap of two p-orbitals

Stereoisomers/geometric isomers

Same molecular formula but different spatial arrangement

Nucleophile

Electron pair donor

Electrophile

Electron pear exceptor

Radical

The species with an unpaired or lone electron

pH

=-log10^H+

Kw

=[H+][OH-]

Buffer solution

A solution that minimizes changes in pH when small amounts of acid or base are added

Enthalpy of atomisation

Enthalpy change when one mole of gaseous atoms is formed from an element in its standard state

Electron affinity

Enthalpy change when one mole of gaseous ions is formed from one mole of gaseous atoms

Lattice enthalpy

The enthalpy change that occurs when one mole of an ionic solid is formed from its gaseous ions

Enthalpy of solution

The anthropy change that occurs when one mole of an ionic compound dissolves in water

Enthalpy of hydration

The enthalpy change that occurs when one mole of gaseous ions forms aqueous/hydrated ions

Entropy

The measure of dispersal of energy in a system

Transition metal

A metal that can form one or more ions that have partially filled d-orbitals

Ligand

A molecule that has at least one lone pair of electrons

Complex ion

A central metal ion surrounded by ligands

Coordination number

How many bonds there are to the metal ion

Monodentate ligand

A ligand with only one lone pair of electrons

Bidentate ligand

A legend with only two lone pair of electrons

Multi or polydentate ligand

A legend with more than two lone pair of electrons

Chiral center

A carbon atom surrounded by four different groups

Optical isomer

Two non superimposable mirror images

A-Amino acid

The NH² and the COOH are attached to the same carbon

Condensation polymerisation

Where by a polymer is produced by repeated condensation reactions between monomers with the removal of a small molecule usually water or HCl

Hydrolysis

The breaking of a bond usually by adding water

TLC

Thin layer chromatography

GC

Gas chromatography

Retention time (chromatography)

How long it takes for a compound to come off the column or to be detected

What does TMS do

TMS also known as tetramethylsilane act as a reference standard in NMR= sharp peak at 0