Definitions Flashcards
Relative Atomic Mass (Ar)
The weighted average of the masses of the isotopes relative to 1/12 of a carbon-12 atom
Relative Molecular Mass (Mr)
The mass of one molecule of a substance relative to 1/12 of the mass of carbon-12 atom
Mass Number
The sum of the protons and neutrons in the nucleus of an atom
Atomic Number
The number of protons in the nucleus of an atom
Isotope
Atoms of the same element with different numbers of neutrons
First Ionisation Energy
The minimum energy required to remove one mole of electrons from an atom in its gaseous state
Electronegativity
A measure of the tendency of an atom in a molecule to attract a binding pair of electrons towards itself
Ligand
An atom, ion or molecule that can donate a pair of electrons to a central metal ion to form a dative covalent (coordinate) bond
[LEWIS BASES]
Exothermic Reaction
A reaction that releases heat to the surroundings
(As a result of forming products with stronger bonds than the reactants. Exothermic reactions have negative ∆H values)
Endothermic Reaction
A reaction that absorbs heat from its surroundings
(As a result of forming products with weaker bonds than the reactants. Endothermic reactions have positive ∆H values)
Standard State
The most stable state of an element or compound under the specified conditions
Standard Conditions
Temperature: 298K
Pressure: 100 kPa (1 atm)
Standard Enthalpy Change of a reaction (ΔH θ)
The heat energy transferred under standard conditions for a reaction
Average Bond Enthalpy
The energy required to break one mole of the same type of bond in the gaseous state averaged over a variety of similar compounds
Standard Enthalpy change of Formation
The enthalpy change when 1 (one) mole of a substance is formed from its elements in their standard states, under standard condtitions
Standard Enthalpy of Combustion
The enthalpy change when 1 (one) mole of a substance in its standard states burns completely in excess oxygen under standard conditions
Lattice Enthalpy
The amount of energy required to separate one mole of ionic compound into isolated gaseous ions under standard conditions
Electron Affinity
The energy change when 1 (one) mole of gaseous atom gains 1 (one) mole of electrons to form a gaseous ion, under standard conditions
Rate of Reaction
The increase in concentration of products or the decrease in concentration of reactants per unit time
Activation Energy
The minimum energy needed (by reactants) to start/initiate a reaction
Arrhenius Acid/Base
Acid is an H+ donor; Base is an OH- donor
Brønsted Lowry Acid
An acid is a proton (hydrogen ion) donor
Brønsted Lowry Base
A base is a proton (hydrogen ion) acceptor
Lewis Acid
An acid is an electron pair acceptor
