Why does CsF have higher solubility but lower melting point than NaF?

[m0286]

Hello, I am doing a grade 12 chemistry course, through independent learning and I am stuck on a question... its probably simple and my mind just doesn't want to work.. so hopefully someone could help me out.

I am given the info that NaF has a solubility of 0.042 kg/kg H20 at 25 C and a melting point of 988 C.
And that CsF has a solubility of 3.67 kg/kg H20 at 25 C and a melting point of 682 C.
So what would be the difference between the properties of CsF and NaF?

 

[p53ud0 dr34m5]

NaF having a smaller radius could account for its higher boiling point. If an atom has a smaller radius, that means the elements are closer together, so more heat is needed to separate them.

 

[dextercioby]

Did u check whether the crystalization system is the same...?As for solubility,it has to do both with the length of the bonding and with the system of crystalization.

Danie.

 

[so-crates]

Because CsF has a lower melting point and higher solubility than NaF, it means that the CsF bond is weaker than the NaF bond. This makes sense since the bond length for NaF is longer than CsF.