Definitions (Understand) Flashcards
Atomic number
the number of protons in the nucleus of an atom
Relative formula mass
the weighted mean mass of a formula unit compared with one-twelth of the mass of an atom of carbon 12
Relative molecular mass
the weighted mean mass of a molecule compared with one-twelfth of the mass of an atom of carbon-12.
Mole
the amount of substance containing as many particles as there are carbon atoms in exactly 12g of carbon-12 isotope
Molar mass
The mass of one mole of any substance, expressed in grams per mole.
Empirical formula
the simplest whole number ratio of atoms of each element in a compound
Molecular formula
the number of atoms of each element in a molecule
Lone pair
an outer-shell pair of electrons that is not involved in chemical bonding
Bonded pair of electrons
A pair of electrons shared between two atoms to make a covalent bond.
Permanent dipole
a small charge difference across a bond resulting from a difference in the electronegativities of the bonded atoms
Polar bond
A covalent bond with a permanent dipole
Polar molecule
a molecule with an overall dipole, taking into account any dipoles across bonds
Alkyl group
an alkane with a hydrogen atom removed, e.g. CH3, C2H5; alkyl groups are often shown as R
Alicyclic
Contains carbon atoms joined together in a ring that is not aromatic.
Aliphatic
Contains carbon atoms joined together in straight or branched chains.
Aromatic
Containing one or more benzene rings
Saturated
Containing single bonds only
Unsaturated
Containing a multiple carbon-carbon bond
Structural isomers
molecules with the same molecular formula but with different arrangements of atoms
Homolytic bond fission
the breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals.
Heterolytic bond fission
the breaking of a covalent bond with both the bonded electrons going to one of the atoms, forming a cation (+ve ion) and an anion (-ve ion)
Radical
a species with an unpaired electron
Stereoisomers
compounds with the same structural formula but with a different arragement of atoms in space.
General formula
the simplest algebraic formula for a member of a homologous series.
Structural formula
a formula showing the minimal detail for the arrangement of atoms in a molecule
Skeletal formula
a simplified organic formula, with hydrogen atoms removed from alkyl chains, leaving just a carbon skeleton and associated functional groups
Displayed formula
a formula showing the relative positioning of all the atoms in a molecule and the bonds between them.
Addition reaction
a reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule.
Electrophilic addition reaction
a type of addition reaction in which an electrophile is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond
Alkane
the homologous series with the general formula CnH2n+2
Alkene
The hydrocarbon homologous series with one carbon-to-carbon and the general formula CnH2n
Structural isomers
molecules with the same molecular formula but with different arrangements of atoms
Elimination reaction
the removal of a molecule from a saturated molecule to make an unsaturated molecule
Dehydration
an elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule.
Carbocation
An ion that contains a positively charged carbon atom.
Average bond enthalpy
the average enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecules of a gaseous species.
Standard conditions
a pressure of 100kPa (1 atmosphere), a stated temperature, usually 298 K (25degrees C), and a concentration of 1 mol dm^-3 (for reactions with aqueous solutions).
Standard state
the physical state of a substance under the standard conditions of 100kPa (1 atmosphere) and 298 K (25 degrees C).
Enthalpy change of reaction
the enthalpy change that accompanies a reaction in the molar quantities expressed the chemical equation under standard conditions, all reactants and products being in their standard states
Homogenous catalyst
a reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state
Heterogenous catalyst
a reaction in which the catalyst has a different physical state from the reactants; frequently, reactants are gases whilst the catalyst is solid.
Hydrogen bond
a strong dipole-dipole attraction between an electron-deficient hydrogen atom (O-H, F-H or N-H) and a lone pair of electrons on a highly electronegative atom (H-O: H-F: or H-N:) on a different molecule
Oxidation
loss of electrons or increase in oxidation number
Substitution
a reaction in which an atom or group of atoms is replaced with a different atom or group of atoms
Volatility
the ease with which a liquid turns into a gas. Volatility increases as boiling point decreases.
Hydrolysis
a reaction with water or aqueous hydroxide ions that breaks a chemical compound into two compounds
