Year 1 definitions Flashcards
Isotope
Atoms of same element with different numbers of neutrons
Atomic (proton) number
Number of protons in the nucleus of an atom
Mass (nucleon) number
Number of particles (protons + neutrons) in the nucleus
Ion
Positively or negatively charge atom or (covalently bonded) group of atoms (a molecular ion)
Relative Isotopic mass
Mass of an atom of an isotope compared with 1/12 the mass of an atom of carbon-12.
Relative Atomic Mass (Ar)
Weighted mean mass of an atom of an element compared with 1/12 the mass of an atom of carbon-12.
Relative Molecular Mass (Mr)
Weighted mean mass of an atom of a molecule compared with 1/12 the mass of an atom of carbon-12.
Relative Formula Mass
Weighted mean mass of a formula unit compared with 1/12 the mass of an atom of carbon-12.
Avogadro Constant
The number of atoms per mole (6.02 X 1023 mol-1)
Mole
The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope.
Molar Mass (Mr)
The mass per mole of a substance. (g mol-1)
Empirical Formula
The simplest whole-number ratio of atoms of each element present in a compound.
Molecule
A small group of atoms held together by covalent bonds.
Molecular Formula
The actual number of atoms of each element in a molecule.
Molar volume
Volume per mole of a gas (dm3mol-1)
At RT&P Molar Volume =24 dm3mol-1
Concentration
The amount of solute (mol) dissolved in 1dm3 of solution
Standard Solution
A solution of a known concentration
Species
Any type of particle that takes place in a chemical reaction.
Stoichiometry
The molar relationship between relative quantities of substance taking part in a reaction.
Acid
A species that is a proton donor.
Base
A species that is a proton acceptor.
Alkali
A base that dissolves in water to form hydroxide ions.
Salt
Any chemical compound formed from an acid when H+ is replaced by a metal or other positive ion.
Cation
A positively charged ion
Anion
A negatively charged ion
Hydrated
Crystalline compound containing water molecules.
Anhydrous
A substance that contains no water molecules.
Water of Crystallisation
Water molecules that form an essential part of the crystalline structure of a compound.
Oxidation Number
A measure of the number of electrons that an atom uses to bond with atoms of another element.
Oxidation
Loss of electrons OR increase in oxidation number
Reduction
Gain of electrons OR decrease in oxidation number
Redox
A reaction in which both reduction and oxidation take place.
Reducing Agent
A reagent that reduces (adds electrons to) another species.
Oxidising agent
A reagent that oxidises (takes electrons from) another species.
First ionisation energy
The energy required to remove one electron from each atom (of an element) in one mole of gaseous atoms from one mole of gaseous 1+ ions
Electron shielding
The repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the positive nucleus on the outer shell electrons
Successive ionisation energies
The measure of energy required to remove each electron in turn. Eg second ionisation energy of an element is the energy required to remove an electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions.
Shell
A groups of atomic orbitals with the same principal number, n.
Principal quantum number
A number representing the relative overall energy of each orbital, which increase with distance from the nucleus.
Atomic orbital
A region within an atom that can hold up to 2 electrons, with opposite spins.
Sub-shell
A group of the same type of atomic orbitals (s, p, d, or f) within a shell
Electron configuration
The arrangement of electrons in an atom.
Compound
A substance formed from 2 or more chemically bonded elements in a fixed ratio.
Ionic Bond
The electrostatic attraction between oppositely charged ions.
Giant ionic lattice
A 3-D structure of oppositely charged ions, held together by strong ionic bonds.
Group
A vertical column in the Periodic Table, with elements of similar properties and the same number of outer shell electrons.
Covalent Bond
A bond formed by a shared pair of electrons.
Lone pair
An outer shell pair of electrons that is not involved in chemical bonding
Dative Covalent Bond (Coordinate)
A shared pair of electrons which has been provided by one of the bonding atoms only.
Electronegativity
A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond
Permanent dipole
A small charge difference across a bond that results from the difference in electronegativity of the bonded atoms
Polar covalent bond
A permanent dipole.
Intermolecular Force
An attractive force between neighbouring molecules.
Permanent dipole-dipole
A weak attractive force between permanent dipole in neighbouring molecules.
Van der Waal’s forces
Attractive forces between induced dipoles in neighbouring molecules.
Hydrogen bond
A strong dipole-dipole attraction between an electron deficient hydrogen in one molecule and a lone pair of electrons on a highly electronegative atom in a different molecule.
Metallic bonding
Electrostatic attraction between positive metal ions and delocalised electrons
Giant Metallic lattice
3-D Structure of positive ions and delocalised electrons bonded together by strong metallic bonds
Simple molecular lattice
3-D structure of molecules bonded together by weak intermolecular forces.
Giant Molecular lattice
3-D structure of atoms, bonded together by strong covalent bonds.
Delocalised electrons
Electrons that are shared between more than 2 atoms
Periodicity
The regular variation of elements with atomic umber and position in the periodic table.
Thermal decomposition
breaking of chemical substance with heat into at least 2 chemical substances.
Displacement reaction
A reaction in which more reactive element displaces a less reactive element from an aqueous solution of the latters ions.
Disproportionation
The oxidation and reduction of the same element in a redox reaction.
Precipitation reaction
The formation of a solid from a solution during a chemical reaction. Precipitates are often formed when 2 aqueous solutions are mixed together.
Nomenclature
Is a system for naming compounds
Unsaturated Hydrocarbon
A hydrocarbon containing at least one carbon-carbon double bond.
Homologous series
Is an organic series with the same functional group but with each member differing by CH2
Functional Group
Is part of an organic molecule responsible for its chemical properties
Alkane
The homologous series without double bonds and the general formula - cnh2n+2
Alkene
The homologous series with a double bond and the general formula - cnh2n
Displayed formula
Shows the relative positions of all atoms in a molecule with bonds between them
Structural formula
Shows minimal detail of the arrangement of atoms in a molecule
Skeletal Formula
Formula with hydrogen’s removed and only the bonds between carbon atoms show, not the atoms themselves.
Structural Isomers
Isomers with the same molecular formula but a different structural formula
Positional isomerism
A type of structural isomerism. When a functional group is on a different numbered carbon,
Chain isomerism
A type of structural isomerism. When branches occur in a chain.
Stereo isomers
Isomers with the same structural formula but a different arrangement in space around a double bond.
E/Z isomerism
A type of stereo isomerism. Double bond stops rotation and different groups on the carbons of this double bond
Homolytic Fission
When a covalent bond breaks giving an electron to each atom creating 2 radicals.
Hetrolytic fission
When a covalent bond breaks and give both electrons to 1 atom forming 1 positive and 1 negative ion.
Radical
A species with an unpaired electron
Nucleophile
(nucleus loving) An electron pair Donator.
Electrophile
(electron loving) an electron pair Acceptor
Addition reaction
When a species ADDS to another species. Requires a double bond
Substitution reaction
When a species REPLACES another species in a reaction.
Elimination reaction
When a molecule is REMOVED from another molecule forming a double bond
Nucleophile substitution
When a nucleophile replaces a halogen.
Free radical Substitution
When a halogen replaces a H in a reaction. 3 steps I,P,T
Electrophilic Addition
When a species ADDS across a double bond.
Fractional distillation
When crude oil is split into its components by their boiling points
Cracking
When a long chain alkane are split into a shorter alkane and an alkene
Combustion
When a compound is burnt completely in oxygen to form carbon dioxide and water
Incomplete combustion
When a compound is burnt in oxygen to form carbon, or carbon monoxide, and water.
Pi bond
Formed by the sideways overlap of adjacent p orbitals - always use diagram.
Polymer
Long chain of monomers
Monomer
Small monomer, usually a alkene, used to build up a polymer
Volatility
Is the ease that a liquid turns into a gas. Volatility increases as boiling point decreases.
Oxidation
When oxygen is added to a molecule
Oxidising agent
Acidified potassium dichromate
Reflux
Used to make primary alcohols into carboxylic acids or secondary into ketones
Distillation
Used to make primary alcohols into aldehydes or secondary into ketones.
Ester
Formed when an alcohol and carboxylic acid react. -(C=O)-O-(CH2)-
Esterification
Is the reaction between an alcohol with a carboxylic acid to produce ester and water.
Dehydration
Is an elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule.
Hydrolysis
Is the reaction with water or aqueous hydroxide ions that breaks a chemical bond into two compounds.
Percentage yield
Found by moles product/moles of reactant x100.
Atom economy
Mr of desired product/Mr of all products x100
IR spectroscopy
Shows the absorption of IR radiation by bonds to show what bonds are present in a sample
Mass spectrometry
Shows the mass/charge for fragments of a molecule
MS fragment
A piece of the molecule broke in MS. Allows us to piece together the starting molecule.
Enthalpy, H
The heat energy stored in a chemical system
Exothermic
When the enthalpy is smaller at then end of a reaction than at the beginning. Resulting in heat loss. Deltah -ve.
Endothermic
When the enthalpy is greater at then end of a reaction than at the beginning. Resulting in heat being taken in. Deltah +ve.
Activation energy
Minimum energy required to start a reaction by the breaking of bonds.
Enthalpy profile diagram
Shows the enthalpy of the reactants and products along with the activation energy and enthalpy change.
Standard conditions
Pressure of 100kpa and Temperature of 298K. In solution concentration of 1M.
Standard state
The state we find a substance in under standard conditions.
Standard enthalpy change of reaction
Is the enthalpy change that accompanies the moles given in a balanced equation are reacted under standard conditions and in standard states
Standard enthalpy change of combustion
Is the enthalpy change when one mol of reactant is burned completely in oxygen under standard conditions
Standard enthalpy change of formation
Is the enthalpy change when 1 mol of product is formed from its constituent elements in standard states under standard conditions.
Specific heat capacity, C
Energy required to heat 1g of substance by 1K.
Bond enthalpy
Is the enthalpy change when 1 mol of given bonds is broken by homolytic fission in a gaseous state.
Hess’ Law
“if a reaction can take place by more than 1 route and the initial and final conditions are the same, the total enthalpy change is the same for each route.”
Rate of reaction
The change in concentration of a reactant or product in a given time.
Catalyst
A species than lowers the activation energy of a reaction by providing an alternate route but is not used itself.
Boltzmann distribution
Is the distribution of energies of molecules within a sample at a given temperature.
Dynamic equilibrium
An equilibrium in a closed system where the rate of forward reaction equals that of the reverse reaction leaving constant concentrations of products and reactants.
Le chatelier’s principle
When a change is imposed on a system in dynamic equilibrium the position of the equilibrium will change to minimise the change.
Greenhouse effect
The process by which absorption and subsequent emission of ir radiation by atmospheric gasses warms the lower atmosphere and the planet’s surface
Troposphere
Lowest layer of earths atmosphere surface to between 7km & 20km
Stratosphere
Second layer of atmosphere contains ozone layer. From troposphere to ~50km
Adsorption
Process by which a gas, liquid or solute is held to a solid surface - such as in a catalytic convertor.
Delocalised electrons
shared between more than two atoms.
Curly arrow
a symbol used to show the movement of an electron pair.
Stem
the longest carbon chain present in an organic molecule.
Redox reaction
one where both reduction and oxidation takes place.
Nucleophile
a species which is attracted to electron deficient centres, where it donates an electron pair to form a new covalent bond.
Esterification
the reaction between a carboxylic acid and an alcohol to form a ester and water.
Hydrolysis
a reaction with water or hydroxide that breaks a chemical compound into two compounds.
Peptide
a compound made of amino acids linked by peptide bonds.
Zwitterion
a dipolar ion of an amino acid that is formed by the donation of a hydrogen ion from the carbonyl group to the amino group. Both charges are present but there is no overall charge.
Isoelectric point
the pH value at which the amino acid exist as a zwitterion.
Condensation reaction
one where two molecules react to from a large molecule with the elimination of a small molecule such as water.
Stereoisomerism
species with the same structural formula but a different arrange moment in space.
Chiral carbon
a carbon bonded to 4 different atoms or group of atoms
Optical isomerism / enantiomers
stereoisomers that are non-superimposable mirror images of each other
Biodegradable polymer
polymer that breaks down completely into carbon dioxide and water
Degradable polymer
polymer that breaks down into smaller fragments when exposed to light, heat or moisture
Phase
a physically distinctive form of a substance, such as the solid, liquid or gaseous states of ordinary matter
Mobile phase
the phase that moves in chromatography
Stationary phase
the phase that doesn’t move in chromatography.
Chromatogram
a visible record showing the result of separation of the components of a mixture by chromatography.
Rf
distance moved by component/distance moved by solvent front
Retention time
(in gas chromatography) - the time for a component to pass from the column inlet to the detector.
Chemical shift
a scale that compares the frequency of an NMR absorption with the frequency of the reference peak of TMS at δ = 0ppm
Rate of reaction
the change ion concentration of a species per unit time
Initial rate of reaction
change of concentration of a species per unit time, at the start of a reaction.
Half life
(of a reactant) - the time taken for the concentration of the reactant to reduce by half.
Reaction mechanism
series of steps that make up the overall reaction
Rate determining step
slowest step in the a multi- step reaction mechanism
Intermediate
a species formed in one step of a multi- step reaction that is used up in the next step so is not seen as a product or reactant in the overall reaction
Equilibrium law
aA +bB cC + dD
Kc= [C]c[D]d / [A]a[B]b
dynamic equilibrium
exist in a closed system when the rate of reaction is equal to the rate of reverse reaction
Homogeneous equilibrium
an equilibrium where all species are in the same physical state
Neutralistaion
a chemical reaction in which an acid and a base react together to produce salt and water
Lattice enthalpy
the enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions
Enthalpy change of formation
enthalpy change when 1 mole of compound is formed from its elements under standard conditions
Enthalpy change of atomisation
the enthalpy change that takes place when 1 ole of gaseous atoms forms from the elements in standard states
Ionisation energy
energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of 1+ ions
Standard enthalpy change of solution
enthalpy change when 1 mole of compound is completely dissolved in water under standard conditions
Standard enthalpy change of hydration
enthalpy change when 1 mole of isolated gaseous ions is dissolved in water forming 1 mole of aqueous ions under standard conditions
Entropy
the quantum measure of degree of disorder in a system
(Gibbs) Free energy change
ΔG is the balance between enthalpy and entropy and temperature for a process.
ΔG = ΔH – TΔS. For a process to take place ΔG <0.
Standard electrode potential
of a half cell, Eθ, is the emf of a half cell when compared to the standard hydrogen half cell, measured under standard conditions.
Transition element
an element in the d – block of the periodic table that forms an ion with an incomplete d sub-shell.
Complex ion
a transition metal ion bonded to one or more ligands by coordinate (dative covalent) bonds
Ligand
a molecule or ion that can donate an electron pair to a metal ion to form a coordinate bond
Coordination number
the number of coordinate bonds a metal ion can have with its ligands
Ligand substitution
a reaction in which one ligand in a complex ion is replaced by another ligand
Stability constant
k stab =is the equilibrium existing between a transition metal ion surrounded by water ligands and the complex formed when the same ion has undergone ligand substitution
