Definitions

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metallic bonding

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is the attraction between the lattice of positive ions and delocalised electrons

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an ionic bond

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is the electrostatic attraction between oppositely charged ions

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ionic bonding

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is a chemical link between two atoms caused by the electrostatic force between a metal and non-metal

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covalent bonding

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the electrostatic attraction between a shared pair of electrons and positively charged nuclei

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dative covalent bond

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is a bond where both electrons originate from the same atom

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allotropes

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different physical forms of the same element

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Valence Shell Electron Pair Repulsion (VSEPR)

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charge centres will arrange themselves as far apart as possible around a central atom to minimise repulsion

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electronegativity

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is the ability of the atom to attract electrons in a covalent bond

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intermolecular forces

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are the forces of attraction found between molecules

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standard enthalpy change OF FORMATION

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enthalpy change on the formation of one mole of a substance from its elements in their standard state under standard conditions

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standard enthalpy change OF COMBUSTION

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enthalpy change on the complete combustion in oxygen of 1 mole of a substance under standard conditions

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standard enthalpy change OF REACTION

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heat transferred in a reaction under standard conditions

e.g Na(s) + 1/2Cl2 --> NaCl(s)

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enthalpy

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is the heat energy content of a amterial

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exothermic reaction

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the reactants give out heat to the surroundings whose temperature increases

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endothermic reaction

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reactants take in energy from the surroundings. The temperature of surroundings decrease

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bond enthalpy

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is the energy required to break one mole of bonds in the gaseous state under standard conditions

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Hess's law

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the enthalpy change for a reaction is independent of the route taken as long as the initial and final conditions are the same

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entropy

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is a measure of randomness or disorder in a system

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free energy change

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is the net driving force of a chemical reaction i.e whether the reaction will be spontaneous or not

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lattice enthalpy

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in an ionic compound it is the heat energy RELEASED when one mole of SOLID in its standard state is FORMED from its IONS in GASEOUS state.
e.g Na+(g) + Cl- (g) --> NaCl(s)

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first ionisation energy

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energy required to REMOVE one mole of ELECTRONS from one mole of ATOMS in the GASEOUS state

e.g Na(g) --> Na+(g) + e-

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second ionisation energy

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is the energy required to REMOVE one mole of ELECTRONS from one mole of GASEOUS +1 IONS

e.g Na+(g) --> Na2+ + e-

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standard enthalpy OF ATOMISATION

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is the enthalpy change on the FORMATION of one mole of GASEOUS ATOMS from the ELEMENT in natural state

e.g Na(s) --> Na(g) // 1/2Cl2(g) --> Cl(g)

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first electron affinity

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is enthalpy change when one mole of ATOMS GAIN one mole of electrons in their GASEOUS state

e.g O(g) + e- --> O-

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second electron affinity

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the enthalpy change of one mole of GASEOUS -1 IONS to gain one mole of ELECTRONS

e.g O-(g) + e- --> O2- (g)

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reversible reaction

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can take place in either direction but will always reach a position of equilibrium

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the position of equilibrium

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is the extent of reaction can lie towards the products (rhs) or reactants (lhs)

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Le Chatelier's principle

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when a change is made to a system in dynamic equilibrium, the position of equilibrium changes to minimise it

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Kc

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is a constant at constant temperature. A change in temperature is the only thing that affects the value of Kc