Answer:
Decreasing order of melting point:
SrS > > RbCl > CsBr
Explanation:
Born–Landé equation explained the relation between lattice energy, charges and sizes of ions present in a compound.
Here, U is internal energy, are charges and is the size.
More the lattice energy more will be the energy to break ionic lattice in order to melt.
Therefore, more the lattice energy, more will be melting point.
Moreover, lattice energy is proportional to charge and inversely proportional to size.
Consider the compounds given
In
In CsBr, charges are
In RbCl charges are
In Srs, charges on ions are
Order of the sizes are as follows:
Cs > Rb
Br > Cl
Cs > Sr
Therefore, decreasing order of melting point:
SrS > > RbCl > CsBr