DEFINITIONS Flashcards
Atomic number (Z)
The number of protons in the nucleus of an atom of that element
Mass number
The sum of the number of protons and the number of neutrons in the nucleus of that atom
Isotope
Atoms of the same element with different masses ( different number of neutrons )
Relative atomic mass (Ar)
The weighted mean/average mass of an atom of an element compared to 1/12 of the mass of an atom of carbon-12
Relative isotopic mass
The mass of an individual atom of a particular isotope relative to 1/12 of the mass of an atom of carbon-12
Molecular ion peak
The peak with the highest m/z ratio in the mass spectrum; the M peak
Quantum shell
Defines the energy level of an electron
Orbital
A region within an atom that can hold up to two electrons with opposite spins
Electronic configuration
The number of electrons in each sublevel in each energy level of the atom
Hund’s rule
States that electrons will occupy the orbitals singly before pairing takes place
Pauli Exclusion Principle
States that two electrons cannot occupy the same orbital unless they have opposite spins
First ionisation energy
The energy required to remove an electron from each atom in one mole of atoms in the gaseous state
Second ionisation energy
The energy required to remove an electron from each singly charged positive ion in one mile of positive ions in the gaseous state
Groups
The vertical columns in the Periodic Table
Periods
The horizontal rows in the Periodic Table
Blocks
The Periodic Table is divided into three ; s-block , p-block and d-block
Periodicity
A regular repeating pattern of atomic, physical and chemical properties with increasing atomic number
Delocalised electrons
Electrons that’s are not associated with any single atom or any single covalent bond
Metallic bonding
The electrostatic force of attraction between the nuclei of metal cations and delocalised electrons
Fragmentation
The process is mass spectrometry that causes a positive ion to split into pieces, one of which is a positive fragment ion, which will be registered at the detector.
Hydrocarbon
A compound that contains only carbon and hydrogen atoms
Saturated
A compound containing only single bonds
Unsaturated
A compound containing one or more multiple bonds
Multiple bonds
Two or more covalent bonds between two atoms
Displayed formula
Shows every atom and every bond
Structural formula
Shows ( unambiguously ) how the atoms are joined together
Skeletal formula
Shows all the bonds between carbon atoms
Molecular formula
Shows the actual numbers of each atom in the molecule
Empirical formula
Shows the numbers of each atom in the simplest whole number ratio
Functional group
An atom or group of atoms in a molecule thats is responsible for its chemical reactions
Homologous series
A family of compounds with the same functional group which differ in formula by CH2 from the next member
Structural isomers
Compounds with the same molecular formula but with different structural formulae
Stereoisomers
compounds with the same structural formula (and molecular formula) but the atoms or groups arranged differently in three dimensions
Geometric isomers
Compounds containing a C=C bond with atoms or groups attached at different positions
Restricted rotation
When a C=C bond fixes the position of the atoms or groups attached to the C=C atoms
Fractional distillation
The process used to separate a liquid mixture into fractions by boiling and condensing
Cracking
The breakdown of molecules into shorter ones by heating with a catalyst
Reforming
The conversion of straight-chain hydrocarbons into branched chain and cyclic-hydrocarbons
Complete combustion
Means that all the atoms in the fuel are fully oxidised
Incomplete combustion
Means that some of the atoms in the fuel are not fully oxidised
Biofuels
Fuels obtained from living matter that has died recently
Renewable
Sources that can be continuously replaced
Non-renewable
Sources that are not being replenished, except over geological timescales
Biodiesel
A fuel made from vegetable oils obtained from plants
Bioalcohols
Fuels made from plant matter, often using enzymes or bacteria
Substitution reaction
One in which an atom or group is replaced by another atom or group
Mechanism
The sequence of steps in an overall reaction. Each step should what happens to the electrons involved in bond breaking or bond formation.
Homolytic fission
The breaking of a covalent bond where each of the bonding electrons leaves with one species, forming a radical
Radical
A species that contains an unpaired electron
Initiation
Step that involves the formation of radicals, usually as a result of bond breaking caused by ultraviolet radiation
Propagation
The two steps that , when repeated many times over , concert the starting materials into the products of a reaction