1 mole of any substance has the same number of particles as 12g of carbon-12.
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Atomic radius
The distance between the nucleus and the outer most electron of an atom
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Ionic radius
The distance between the nucleus and the outer most electron of an ion
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Periodicity
The repeating patterns of chemical and physical properties shown by elements across the periods
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Hydrophobic
A substance that “likes” water; is able to be dissolved in water.
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Hydrophilic
A substance that “dislikes” water; is unable to be dissolved in water.
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The law of conservation of energy
Energy cannot be created or destroyed. It can only be transformed from one form of energy to another.
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Hess’s Law
The total enthalpy change in a chemical reaction is independent of the route by which the chemical reaction takes place as long as the initial and final conditions are the same.
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Enthalpy Change of Reaction
The enthalpy change when the reactants in the stoichiometric equation react to give the products (under standard conditions)
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Enthalpy Change of Formation
The enthalpy change when 1 mole of a compound is formed from its elements (under standard conditions)
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Enthalpy Change of Combustion
The enthalpy change when 1 mole of a substance is reacted/burnt in excess oxygen (under standard conditions)
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Enthalpy Change of Neutralisation
The enthalpy change when 1 mole of water is formed by reacting and acid with an alkali (under standard conditions)
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Enthalpy Change of Hydration
The enthalpy change when 1 mole of a specified gaseous ion dissolves in sufficient water to form a very dilute solution (under standard conditions)
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Enthalpy Change of Solution
The enthalpy change when 1 mole of an ionic solid compound fully dissolves in sufficient water to form a very dilute solution (under standard conditions)
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Enthalpy Change of Atomisation
The enthalpy change when one mole of gaseous atoms is formed from its element (under standard conditions)
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Bond Energy
The energy required to break one mole of a particular covalent bond in the gaseous states (under standard conditions)
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Bond Length
the internuclear distance of two covalently bonded atoms (the distance from the nucleus of one atom to another atom that forms the covalent bond)
(under standard conditions)
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Standard Conditions
Pressure of 101kPa and a temperature of 298 K (25 ℃)
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Exothermic Reactions
A reaction is exothermic when the products have less energy than the reactants.
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Endothermic Reactions
A reaction is endothermic when the products have more energy than the reactants.
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The Pauli Exclusion Principle
No two electrons can be identified by the same set of quantum numbers. In other words, two electrons in an orbital must have opposite spins.
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Ground state
The most stable electronic configuration of an atom which has the lowest amount of energy.
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Nucleon Number
The number of protons and neutrons (excludes number of electrons)
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First ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms of a specific element (under standard conditions)
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Second ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous ions of a specific element (under standard conditions)
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Dynamic equilibrium
The molecules or ions of reactants and products are continuously reacting.
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Equilibrium position
The balance point where the amount of reactants and products formed remains constant.
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Le Chatelier’s Principle
When a chemical system in dynamic equilibrium is disturbed (conditions change), the system tends to shift the equilibrium to oppose the change and a new equilibrium is set up.
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Collision theory
For a chemical reaction to occur, particles of the reactants must collide with sufficient energy and at the correct orientation.
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Mole fraction
The mole fraction for a specific gas in chemical reaction is the amount of moles of that gas divided by total number of moles of gases
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Partial Pressure
Partial Pressure of a specific gas in a mixture is the pressure which it would exert if it occupied the whole container alone.
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The Contact Process
The Contact process makes sulphur dioxide – which converts sulphur dioxide into sulphur trioxide (reversible reaction) – which then converts sulphur trioxide into concentrated sulfuric acid.
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The Haber Process
The Haber process creates ammonia by combining nitrogen from the air with hydrogen derived from methane gas.
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Catalyst
A substance used to reduce/lower the activation energy of a chemical reaction
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Oxidation
Oxidation is a loss of electrons. Oxidation is an increase in oxidation number.
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Reduction
Reduction is a gain in electrons. Reduction is a decrease in oxidation number.
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Oxidising agent
A substance that oxidises another atom or ion by causing it to lose electrons.
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Reducing agent
A substance that reduces another atom or ion by causing it to gain electrons
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Disproportionation reaction
When a substance undergoes oxidation and reduction in the same reaction
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Bronsted-Lowry theory
Acids can be defined as proton donors. A base can be defined as a proton acceptor.
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Ionisation of a compound
The process in which a neutral molecule splits/dissociates into charged ions when exposed in a solution.
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Amphoteric
A substance that can act as both a base and an acid
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Volatility
How easily a substance can evaporate
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Functional Groups
The atom, group of atoms, or structural feature in a molecule that is the site of reactivity
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Aliphatic Compounds
Compounds which do not have aromatic rings (benzene).
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Homologous series
A family of organic compounds that have similar features and chemical properties due to having the same functional groups.
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Chiral Centre
The asymetric central carbon atom is bonded to 4 different functional groups
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Enantiomer
Two optical isomers
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Racemic mixture
A mixture of enantiomers
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Saturated Hydrocarbons
Hydrocarbons that only contain (C-C) carbon single bonds
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Unsaturated Hydrocarbons
Hydrocarbons that contain one or more (C=C) carbon double bonds or carbon triple bonds
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Homolytic Fission
Breaking of a covalent bond in such a way that each atom takes half the number of electrons from the bond to form 2 radicals
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Heterolytic Fission
Breaking of a covalent bond in such a way that the more electronegative atom takes the electrons from the bond to form a negative ion and leaving behind a positive ion
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Nucleophile
An electron-rich species that can donate a pair of electrons
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Electrophile
An electron-deficient species that can accept a pair of electrons
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Monomer
A molecule, generally organic, that can react with other molecules to form very large molecules called polymers
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Polymer
A large molecule made up of a very large number of repeating units called monomers
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Markovnikov’s Rule
When a hydrogen halide compound (H-X) is added to an unsymmetrical alkene, the hydrogen becomes attached to the carbon with the most hydrogen attached to it already
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Zaitsev’s rule
Elimination will occur such that the hydrogen is removed from the carbon with the least hydrogens
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Lattice Energy
The enthalpy change when one more of an ionic compound is formed from its gaseous ions (under standard conditions)
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The first Electron Affinity
The enthalpy change when 1 mole of electrons is added to 1 mole of gaseous atoms, to form 1 mole of gaseous ions each with a single negative charge (under standard conditions)
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Entropy of a given system
The number of possible arrangements of the particles and their energy in a given system
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Electrolysis
The process by which ionic compounds are decomposed/broken down into simpler substances when an electric current passes through them
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Electrode Potential
The electrode (reduction) potential E is a value which shows how easily a substance is reduced.
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The standard electrode potential (Eꝋ)
The voltage produced when a standard half-cell is connected to a standard hydrogen cell under standard conditions
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The standard cell potential (Ecellꝋ)
The voltage difference between two standard half-cells
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The acidic dissociation constant
The equilibrium constant for the dissociation of a weak acid at 298K.
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The ionic product of water
The equilibrium constant for the dissociation of water at 298K which has a value of 1.00x10-14 mol2dm-6.
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Buffer solution
A solution in which the pH does not change a lot when small amounts of acids or alkalis are added.
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Solubility
The maximum amount of solute that can be dissolved into a known amount of solvent at a given temperature, producing a saturated solution
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Solubility product
The product of the concentrations of each ion in a saturate solution of a relatively soluble salt, at 298K, raised to the power of their relative concentrations
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Saturated Solution
A solution that contains the maximum amount of dissolved salt
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Partition coefficient (Kpc)
The ratio of the concentrations of a solute in two different immiscible solvents in contact with each other when equilibrium has been established
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Half-life
The time taken for the concentration of a limiting reactant to become half of its initial value
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A complex molecule/ion
A molecule/ion formed by a central metal atom/ion surrounded by one or more ligands
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Ligand
A molecule/ion that has one or more lone pairs of electrons
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Monodentate ligand
Form only one dative bond to the central metal ion
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Bidentate ligand
Form 2 dative bonds to the central metal ion
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Polydentate ligand
Form more than 2 dative bonds to the central metal ion
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Ligand exchange/substitution
When one ligand complex is replaced by another
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The stability constant
The equilibrium constant for the formation of the complex ion in a solvent from its constituent ions or molecules
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