AS chemistry definitions Flashcards
“isotope”
Isotopes are atoms of the same element that contain the same number of protons and electrons but a different number of neutrons
first ionisation energy
The first ionisation energy (IE1) is the energy required to remove one mole of electrons from one mole of atoms of an gaseous state element to form one mole of gaseous state 1+ ions
“unified atomic mass”
“one twelfth of the mass of a carbon-12 atom”
“relative atomic mass”
relative atomic mass (Ar) of an element is the weighted average mass of the atoms in a given sample of an element compared to the unified atomic mass unit
relative isotopic mass
The relative isotopic mass is the mass of a particular atom of an isotope compared to the value of the unified atomic mass unit
“relative molecular mass”
The relative molecular mass (Mr) is the ratio of weighted average mass of a molecule of a molecular compound to the unified atomic mass unit
relative formula mass
The relative formula mass is the weighted average mass of one formula unit compared to the unified atomic mass unit
Avogadro constant
The Avogadro constant (NA or L) is the number of particles equivalent to the relative atomic mass or molecular mass of a substance.
empirical formula
the simplest whole number ratio of the elements present in one molecule or formula unit of a compound
“molecular formula”
“formula that shows the number and type of each atoms in an molecule”
“electronegativity”
“power of an atom to attract electrons to itself”
ionic bonding
electrostatic attraction between oppositely charged ions (positively charged cations and negatively charged anions)
metallic bonding
“electrostatic attraction between positive metal ions and delocalised electrons”
“covalent bonding”
“electrostatic attraction between the nuclei of two atoms and a shared pair of electrons”
“bond energy”
“the energy required to break one mole of a particular covalent bond in the gas state”
bond length
” internuclear distance of two covalently bonded atoms”
“standard conditions “
temperature of 273 K and pressure 1atm
enthalpy change of reaction
ΔHr
“the enthalpy change when the reactants in the stoichiometric equation react to give the products under standard conditions”
enthalpy change formation
ΔHf
“the enthalpy change when one mole of a compound is formed from its elements under standard conditions”
enthalpy change combustion
ΔHc
“the enthalpy change when one mole of a substance is burnt in excess oxygen under standard conditions”
enthalpy change of neutralisation
ΔHneut
“the enthalpy change when one mole of water is formed by reacting an acid and an alkali under standard conditions”
“Le Chatelier’s principle”
Le Chatelier’s principle says that if a change is made to a system at dynamic equilibrium, the position of the equilibrium moves to minimise this change.
“activation energy”
EA
The activation energy is the minimum amount of energy that particles require in order for a successful collision to occur which will cause the reaction to happen.
hydrocarbon
“compound made up of C and H atoms only”
