Lattice enthalpy
Formation of 1 mole of ionic lattice from its gaseous ions under standard conditions
Exothermic: ionic bond formation
To measure the strength of ionic bonding in a giant ionic lattice
Ionic size
Increases :
Attraction btw ions decreases
= ΔₗₑH less negative
Ionic charge
Increases:
attraction between ions increases
= ΔₗₑH more negative
Enthalpy changes of :
, 2
Atomisation: formation of 1 mole of gaseous atoms from elements in their standard
states under standard conditions
Endothermic: intermolecular forces broken to form gaseous atoms
1st ionisation energy:
Endothermic: energy is put in to overcome the attraction between the negative electron
and positive nucleus
1st electron affinity: 1 electron added to each atom in 1 mol of gaseous atoms to form 1
mol of gaseous 1- ions
Exothermic: electron being added is attracted to the positive nucleus
2nd electron affinity:
Endothermic: 2nd electron being added is repelled by the anion = energy is put in to
force the negative electron onto the negative ion (that already gained an electron)
Born-Haber cycles
● Δ𝑓H = sum of the known enthalpy changes
Formation of 1 mole of ionic lattice from its gaseous ions under standard conditions
Exothermic: ionic bond formation
To measure the strength of ionic bonding in a giant ionic lattice
Ionic size
Increases :
Attraction btw ions decreases
= ΔₗₑH less negative
Ionic charge
Increases:
attraction between ions increases
= ΔₗₑH more negative
Enthalpy changes of :
, 2
Atomisation: formation of 1 mole of gaseous atoms from elements in their standard
states under standard conditions
Endothermic: intermolecular forces broken to form gaseous atoms
1st ionisation energy:
Endothermic: energy is put in to overcome the attraction between the negative electron
and positive nucleus
1st electron affinity: 1 electron added to each atom in 1 mol of gaseous atoms to form 1
mol of gaseous 1- ions
Exothermic: electron being added is attracted to the positive nucleus
2nd electron affinity:
Endothermic: 2nd electron being added is repelled by the anion = energy is put in to
force the negative electron onto the negative ion (that already gained an electron)
Born-Haber cycles
● Δ𝑓H = sum of the known enthalpy changes
