Definitions Flashcards
activation energy
minimum amount of energy needed to start a reaction by the breaking of bonds
alkali
a soluble base which releases hydroxide ions
Atomic orbital
a region of space around the nucleus that can hold up to 2 electrons with opposite spins
bond enthalpy
the energy needed to break one mole of a specified bond in the gas state
buffer solution
a system which minimises PH changed when small amounts of acid or base are added
catalyst
a substance which increases the rate of reaction by providing an alternative route of lower activation energy
covalent bond
electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
d-block element
an atom that has its highest energy electron in a d subshell
dative covalent bond
a shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms
disproportionation
a redox reaction where the same element is oxidised and reduced
dynamic equilibrium
a continous reaction in a closed system where the rate of the forward reaction is the same as the rate of the reverse reaction and the concentrations remain constant
electronegativity
the ability of an atom to attract the pair of electrons in a covalent bond
first ionisation energy
the energy needed to remove on mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions
homogenous catalyst
a catalyst which is in the same physical state as the reactants
heterogenaous
a catalyst which is in a different physical state to the reactants
hydrogen bond
a strong dipole-dipole attraction between an electron deficient hydrogen atom of -NH, -OH, or HF and the lone pair of the N, O, F on a neighbouring molecule
ioinic bond
electrostatic attraction between oppositely charged ions
metallic bond
electrostatic attraction between metal cations and delocalised electrons
rate of reaction
the change in the concentration of a reactant or product in a given time
reducing agent
a species that donates electrons
relative atomic mass
weighted mean/average mass of an atom of an element compared to 1/12th of the mass of an atom of carbon-12
relative isotopic mass
mass of an isotope compared to 1/12th of the mass of an atom of carbon-12
oxidising agent
a species which accpets electrons
simple molecular lattice
a three dimensional structure of molecules held together by imf
standard solution
a solution of known concentration
standard enthalpy change iof combustion
the enthalpy change when one mole of a substance is reacted completely with oxygen under standard conditions
standard enthalpy change of formation
the enthalpy change when one mole of a compound is formed from its constituent elements under standard conditions
standard enthalpy change of neutralisation
the enthalpy change when an acid and base react to form a mole of water under standard conditions
