definitions Flashcards
Atomic number
The number of protons in one atom of an element
Mass number
The sum of the number of protons + the number of neutrons in 1 atom of an element
Isotopes
Atoms of the same element with different numbers of neutrons and, therefore, different masses
Orbital
A region of space around the nucleus of an atom that can be occupied by up to 2 electrons, with opposite spins
First ionisation energy
Energy needed to remove one mole of electrons from one mole of gaseous atoms of an element (X(g) —-> X+(g) + e-)
Ionic bonding
The electrostatic attraction between positive and negative ions
Cation/anion
A cation is a positive ion; and an anion is a negative ion
Covalent bonding
The attraction between a shared pair of electrons and the nuclei of the bonded atoms
Dative covalent bonding
The attraction between the shared pair of electrons and the nuclei of two atoms, with both of the shared electrons are provided by the same atom
Metallic bonding
The attraction between a lattice of positive ions and the sea of delocalised electrons
Electronegativity
The ability of an atom to attract the bonding electrons in a covalent bond
Polar bond
A covalent bond in which the electrons are shared unequally between two atoms, as a result of an electronegativity difference between the atoms involved
Intermolecular forces
Attractive forces between molecules
Relative atomic mass (Ar)
weighted mean mass of an atom of an element relative to 1/12 of the mass of an atom of carbon 12
Relative isotopic mass
Mass of one atom of an isotopes of an element relative to 1/12 of the mass of an atom of carbon 12. (N.B. Not average mass here)
Mole
The amount of a substance that contains the same number of particles as there are atoms in exactly 12 g of carbon 12
Molar mass
The mass of one mole of a substance (i.e.: the mass of the amount of a substance that contains the same number of particles as there are atoms in exactly 12 g of carbon 12)
Avogadro’s constant
The number of particles in one mole of a substance. (Its value is 6.02×10 to the 23 - remember this is given on the data sheet)
Acid
A proton donor (H+ ion) donor. An acid disassociates into ions in water
Base
A proton acceptor
Alkali
A bass that dissolves in water releasing hydroxide ions OH-(aq) into the aqueous solution
Salt
A compound formed when the H+ in acid is replaced by a metal ion or NH4+ ion
Neutralisation
Reaction of an acid with a base to form a salt
Periodicity
A repeating pattern of properties across different periods
Oxidation
Loss of electrons/oxidation state becomes more positive
Reduction
Gain of electrons/oxidation state becomes less positive
Disproportionation
Reaction involving oxidation and reduction of the same element
Standard conditions
1 atm pressure and that the temperature of 25° (unless otherwise stated)
Standard state
The state (solid/liquid/gas) a substance exists in, under standard conditions
Enthalpychange of reaction
Enthalpy change associated with a stated equation
Enthalpy change of formation
Enthalpy change when one mole of a compound is formed from its elements
Enthalpy change combustion
Enthalpy Change for complete combustion of one mole of a substance
Enthalpy change of neutralisation
Enthalpy change when one mole of water is formed in a neutralisation reaction
Average bond Enthalpy
Enthalpy change when one mole of bonds in gaseous molecules are broken (average of this value for a range of substances)
Hess’ law
The Enthalpy change is independent of the route taken
Catalyst
A substance that increases the rate of a reaction without itself being used up. It does this by providing an alternative pathway with a lower activation energy
Homogenius/heterogeneous
In the same phase/in different phases
Le Chatelier’s principle
If the system is at equilibrium and one of the conditions is changed, the equilibrium shifts in the direction that opposes the change
Homologous series
A series of organic compounds all having the same functional group but with each successive member differing by CH2
General formula
And algebraic formula (using n) that represents all the members of a homologous series
Functional group
A group of atoms responsible for the characteristic reactions of a compound
Alkyl group
A part of the molecule with general formula CNH2n+1 (E.g. methyl, ethyl, etc)
Aliphatic
And organic compound or group that does not contain an aromatic ring
Alicyclic
And organic compound or group that contains a non-aromatic ring (e.g. cyclohexene or a cyclohexyl group)
Aromatic
And organic compound or compound containing a benzene ring
Saturated
And organic compound or group with only single bonds between carbon atoms
Unsaturated
And organic compound or group containing multiple bonds between carbon atoms
Structural isomers
Compounds with the same molecular formula but different structural formula
Stereoisomers
Compounds with the same structural formula but different arrangement in space
Homolytic fission
Covalent bond breaking in which each of the bonded atoms receives one electron from the shared pair, forming to radicals
Heterolytic fission
Covalent bond breaking, in which one of the bonded atoms receives both electrons from the shared pair
Sigma minus bond
Covalent bond formed by overlap of orbitals directly between the nuclei of the bonded atoms
Pi minus bond
A covalent bond formed by sideways overlap of P-orbitals, above and below the plane of the bonded atoms
Radical
A species with an unpaired electron
Electrophile
An electron pair acceptor
Nucleophile
An electron pair donor
Hydrolysis
A reaction in which a compound is broken down by reaction with water
Quickfit
Apparatus for carrying out chemical processes, in which bits are connected together via ground glass joints
Volatility
Ease of evaporation
Reflux
A continuous cycle of evaporation, condensation and return to the original vessel
Percentage yield
(Actual yield/maximum possible yield) X 100
Atom economy
(Mr of desired products/some of Mr of all products) X 100
