Definitions (Understand) Flashcards
Ion
a positively or negatively charged atom or (covalently bonded) group of atoms (a molecular ion).
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
Anhydrous
a substance containing no water molecules
Hydrated
crystalline and containing water molecules
Water of crystallisation
water molecules that form an essential part of the crystalline structure of a compound.
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
