Exam Definitions

• Atomic Number: The number of protons in the nucleus of an atom.
• Mass Number: The total number of protons and neutrons in the nucleus of an atom.
• Relative Isotopic Mass: The mass of an isotope relative to 1/12 the mass of a Carbon 12 atom.
• Relative Atomic Mass: Weighted average mass of all the isotopes of an atom relative to 1/12 the mass of one atom of carbon 12.
• Ionisation Energy: The energy required to remove one mole of electrons from one mole of an atom in the gaseous state to form one mole of unipositive gaseous ions.
• Periodicity: A repeating pattern of physical or chemical properties of elements in the periodic table.
• Concentration: The amount of a solute dissolved in a given volume of a solution.
• Empirical Formula: The simplest whole number ratio of atoms of each element present in a molecule.
• Molecular Formula: The actual number of atoms of each element present in a molecule.
• Percentage Yield: A measure of how successful the laboratory preparation of a product has been.
• Atom Economy: A measure of the efficiency of a reaction in terms of the atoms involved.
• Ionic Bond: The electrostatic attraction between oppositely charged ions in a lattice.
• Covalent Bond: The electrostatic attraction between the nuclei of adjacent atoms and one or more shared pairs of electrons.
• Dative Bond: A bond that contains a shared pair of electrons with both electrons donated by one atom.
• Metallic Bond: The attraction between delocalised electrons and positive ions arranged in a lattice.
• Electronegativity: The ability of an atom to attract a bonding pair of electrons in a covalent bond.
• Ductility: The ability of a metal to be drawn out and stretched into thin wires.
• Functional Group: An atom or a group of atoms that give an organic compound its particular chemical properties.
• Hydrocarbons: A molecule made up of C and H atoms only.
• Alkanes: are saturated hydrocarbons as they don't contain any double C-C bonds.
• Alkenes: are unsaturated hydrocarbons as they contain atleast one double C-C bond.
• Aliphatic Hydrocarbons: Contains a chain of C atoms. ( e.g. Butane)
• Alicyclic Hydrocarbons: Contains a ring of C atoms. ( e.g. Cyclopentane)
• Aromatic Hydrocarbons: Contains a benzene ring (e.g. Benzene).
• Structural Isomers: molecules of the same molecular formula but have a different structural formula.
• Stereoisomers: molecules of the same structural formula but different arrangement of atoms in space.
• Chain Isomerism: Molecules have the same molecular formula but their structures have their carbon chains arranged differently.
• Positional Isomerism: Molecules have the same molecular formula, but the functional group occurs on different position on the same carbon skeleton.
• Functional Group Isomerism: Molecules have the same molecular formula but different functional groups.
• Nucleophile: An electron pair donor.
• Nucleophilic Substitution: A reaction where an atom or group of atoms is replaced with a new atom or group of atoms via attack by a nucleophile.
• Hydrolysis Reaction: A reaction where water is used to break a covalent bond.
• Elimination: A reaction which an atom or group of atoms is removed from a reactant molecule.
• Electrophile: An electron pair acceptor.
• Radical: A species with an unpaired electron.
• Fraction: A group of molecules with a boiling point within a similar range due to a similar number of carbon atoms and are removed at the same level from the fractionating column.
• Cracking: Longer less useful hydrocarbon molecules are broken down into smaller, more useful molecules of higher value and higher demand.
• Substitution Reaction: A reaction where a hydrogen atom is replaced by a halogen atom.
• Isotope: Atoms of the same element of different numbers of neutrons but same number of protons in the nucleus.
• Activation Energy: The minimum amount of energy needed for a reaction to occur.