Definitions Flashcards
Define the atomic number
The number of protons
Define an isotope
Atoms of the same element with the same numbers of protons but different numbers of neutrons and masses.
Define the mass number (on periodic table)
The number of protons + the number of neutrons
Define an ion.
A charged atom
Define a cation
A positive ion - atoms with fewer electrons than protons
Define an anion
A negative ion - atoms with more electrons than protons
Define the relative isotopic mass
The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12.
Define the relative atomic mass Ar
The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12.
Define a binary compound
Contains 2 elements only
Define a polyatomic ion
An ion that contains more than 1 element bonded together
Define a diatomic molecule
2 of the same atoms bonded together e.g. O2,Cl2
Define the formula unit
In ionic compounds, the formula worked out from the ionic charges that are used in equations
Define avogadros constant
6.02 x 10^23 mol^-1
The number of particles in each mole of carbon-12
Define molar mass
The mass per mole of a substance in units of g mol^-1
Define the molecular formula
The number of atoms of each element in a molecule
Define the empirical formula
The simplest whole-number ratio of atoms of each element in a compound.
Define the relative molecular mass Mr
Compares the mass of a molecule with the mass of an atom of carbon-12
Define the relative formula mass
Compares the mass of a formula unit with the mass of an atom of carbon-12
Define hydrated
A crystalline compound containing water molecules
Define the water of crystallisation
Water molecules that are bonded into a crystalline structure structure of a compound.
Define anhydrous
Containing no water molecules
Define standard solution
A solution of known concentration
Define molar gas volume
The volume per mole of gas molecules at a stated temperature and pressure.
Define limiting reagent
The reactant that is not in excess and is used up first and stops the reaction.
Define atom economy
A measure of how well atoms have been utilised.
Define a strong acid
An acid that completely dissociates in aq to release H+
Define a weak acid
An acid that partially dissociates in aq to release H+
Define a salt
Product of reaction in which H+ from acid are replaced by metal or ammonium ions.
Define a base
Insoluble compound that neutralises an acid to form a salt.
Define an alkali
A soluble base that dissociates in aq to release OH-
Define titration
A technique use dot accurately measure the volume of one solution that reacts exactly with another solution.
Define a redox reaction
A reaction involving reduction and oxidation
Define principal quantum number
The shell number or energy level number
Define an atomic orbital
A region around the nucleus that can hold up to 2 electrons with opposite spins.
Define sub-shell
A group of orbitals of the same type within a shell
Define an ionic bond
The electrostatic attraction between positive (anions) and negative ions (cations).
Define a covalent bond
The head on strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
Define lone pair of electrons
Paired electrons that are not shared
Define a dative covalent bond (coordinate bond)
A covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only.
Define electronegativity
The attraction of a bonded atom for the shared pair of electrons in a covalent bond.
Define periodicity
A repeating trend in properties of the elements across each period of the periodic table.
Define 1st ionisation energy
The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form 1 mole of gaseous 1+ ions.
Define shielding effect
The repulsion between electrons in different inner shells. Shielding reduces the net attractive force between the positive nucleus on the outer shell electrons.
Define 2nd ionisation energy
The energy required to remove 1 electron from each ion in one mole of gaseous 1+ ions of an element to form 1 mole of gaseous 2+ ions.
Define metallic bonding
The strong electrostatic attraction between positive ions and delocalised electrons.
Define a reducing agent
A reagent that reduces (adds electrons to) another species.
Define a disproportionation reaction
A redox reaction involving which the same element is both reduced and oxidised.
Define enthalpy
A measure of heat energy in a chemical system
Define the law of conservation of energy
Energy cannot be created/destroyed
Define exothermic reaction
A reaction in which the enthalpy of products is smaller than the enthalpy of reactants, resulting in heat loss to the surroundings
Define endothermic reaction
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings.
Define activation energy
Minimum energy required to start a reaction by the breaking of bonds
Define standard pressure
100 kPa
Define standard temperature
298K (25*C)
Define standard concentration
1 mol dm-3
Define standard state
The physical state of a substance under standard conditions.
Define standard enthalpy change of reaction
The enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions, with all reactants and products in their standard states.
Define standard enthalpy change of formation
The enthalpy change that takes place when 1 mole of a compound is formed from its elements under standard conditions with all reactant and products in their standard states.
Define standard enthalpy change of combustion
The enthalpy change that takes place when 1 mole of a substance reacts completely with oxygen under standard conditions, with all reactants and products in their standard states.
Define standard enthalpy change of neutralisation
The energy change that accompanies the reaction of an acid by a base to form 1 mole of H2O(l), under standard conditions, with all reactants and products in their standard states.
Define specific heat capacity
The energy required to raise the temp of 1g of a substance by 1K.
Define average bond enthalpy
Energy required to break 1 mole of a specified type of bond in a gaseous molecule.
Define Hess’ law
If a reaction can take place by more than 1 route and the initial & final conditions are the same, the total enthalpy change is the same for each route.
Define rate of reaction
Change in concentration of a reactant or a product in a given time.
Define a catalyst
A substance that changes the rate of a chemical reaction without undergoing any permanent change itself.
Define homogenous catalyst
A reaction in which the catalyst and reactants are in the same physical state, which’s most frequently the aqueous or gaseous state.
Define heterogeneous catalysts
A reaction in which the catalyst has a different physical state from the reactants, frequently reactants are gases whilst the catalyst is a solid.
Define position of equilibrium
The relative quantities of reactants and products, indicating the extent of a reversible reaction at equilibrium.
Define le chateliers principle
When a system in equilibrium is subjected to an external change the system readjusts itself to minimise the effect of that change.
Define Kc
A measure of the position of equilibrium; the magnitude of an equilibrium constant indicates whether there are more reactants or more products in an equilibrium system.
Define hydrocarbon
Compound containing C and H only.
Define saturated
Single bonds only
Define unsaturated
Contains C-C multiple bonds
Define homologous series
A family of compounds with similar chemical properties whose successive members differ by the addition of a -CH2- group.
Define functional group
The part of the organic molecule that’s largely responsible for the molecule’s chemical properties.
Define aliphatic
C atoms are joined to each other in unbranched (straight) or branched chains, or non-aromatic rings
Define alicyclic
C atoms are joined to each other in ring (cyclic) structures, with or without branches
Define aromatic
Some or all of the C atoms are found in a benzene ring
Define molecular formula
Shows number and type of atoms of each element present in a molecule.
Define empirical formula
The simplest whole number ratio of the atoms of each element present in a compound
Define general formula
The simplest algebraic formula for any member of a homologous series.
Define structural isomer
Compounds with the same molecular formula but different structural formula.
Define radical
Atom/groups of atoms with an unpaired electron
Define homolytic fission
CB breaks, each of bonded atoms take 1 of shared pair of electrons from the bond.
Define heterolytic fission
CB breaks, 1 of bonded atoms takes both of electrons from the bond. To form neg and pos ions.
Define curly arrow
Show movement of electron pairs when bonds are being broken or made.
Define fish arrow hook
Movement of a single unpaired electron
Define addition reaction
2 reactants join together to form 1 product
Define substitution reaction
Atom/group of atoms is replaced by a diff atom or group of atoms.
Define elimination reaction
Involves removal of small molecule from a larger one
Define sigma Bond
The overlap of 2 atomic orbitals, 1 from each bonding atom directly between bonding atoms
Define pi-bond
Sideways overlap of 2 adjacent p-orbitals above and below bonding C atoms, 1 from each C atom of double bond.
Define stereoisomer
Compounds with the same structural formula but with a different arrangement of atoms in space.
Define electrophiles
Electron pair acceptor
Define carbocation
Ion that consists a pos charged C atom
Define polymer
Large molecule formed from many thousands of repeat units of smaller molecules known as monomers.
Define addition polymerisation
Formation of a very long molecular chain, by repeated addition reactions of many unsaturated alkene molecules (monomers).
Define monomer
Small molecule that combines with many other monomers to form a polymer.
Define repeat unit
The specific arrangement of atoms in polymer molecule that repeats over and over again.
Define dehydration
An elimination reaction in which H2O id removed from a saturated molecule to make an unsaturated molecule.
Define nucleophile
Electron pair donor
Define hydrolysis
Reaction with H2O that breaks a chemical compound into 2 compound, the H and OH in a water molecule becomes incorporated into the 2 compounds
Define molecular ion
Pos ion formed in mass spectrometry when a molecule loses an electron
Define M + 1 peak
The very small peak one unit after the M+ peak which exists because 1.1% of C is present as C-13 isotope.
Define fragmentation
Process in mass spectrometry that causes a pos ion to split into smaller pieces, 1 of which is a pos fragment ion.
Define fragment ion
Ions formed from breakdown of molecular ion in a mass spectrometer
Define finger print region
An area of an infrared spectrum below 1500cm-1 that gives a characteristic pattern for different compounds.
Define half-life
Time taken for conc of reactant to decrease by half
Define rate-determining step
Slowest step in reaction mechanism of a multi-step reaction
Define homogeneous equilibrium
An equilibrium in which all species making up reactants and products have same physical state
Define heterogeneous equilibrium
An equilibrium in which the species making up reactants & products have different physical states.
Define partial pressure
The contribution that the gas makes towards total pressure.
Define bronsted Lowry acid
Proton donor
Define bronsted Lowry base
Proton acceptor
Define conjugate acid-base pairs
Define (mono-,di-,tri-) -basic acids
Define acid dissociation constant Ka
Define ionic product of water
Define a buffer solution
Define equivalence point
Define end point
Define esterification
Reaction of an alcohol with carboxylic acid to Form an ester
