In: Chemistry
Pick the compound with the biggest lattice energy:
1) LiI or CsI
2) SrS or SrCl2
Lattice energy is defined as the energy required to separate a mole of an ionic solid into gaseous ions.
Two main factors that contribute to the magnitude of the lattice energy are the charge and radius of the bonded ions. Lattice Energy is directly proportional to charge on cation/anion and inversely proportional to bond length (center-to-center distance of cation and anion atoms) or radius of atoms.
For example :
1) same charge and different radius or size of cation
LiCl > NaCl > KCl > RbCl > CsCl
NaF > NaCl > NaBr > NaI
MgO > CaO > SrO
2) Charge is more dominating factor than size for lattice energies
MgO > NaF
Mg = +2 , O = -2
Na = +1 , F = -1
Answer for 1) LiI is having larger lattice energy than CsI
Answer for 2) SrS is having larger lattice energy than SrCl2