Why is melting point of $\ce{Mg3N2}$ lower than that of $\ce{Be3N2}$ ?
I have two reasonings:
- The lattice energy of $\ce{Be3N2}$ is higher than that of $\ce{Mg3N2}$ so accordingly the melting point of the former should be higher
- Both of them form ionic nitrides. Since $\ce{Mg3N2}$ has more ionic character it should have higher melting point than $\ce{Be3N2}$
Since both of these are contradicting, I wish to ask which one is correct? And if both are correct in some way, which one should be prioritized over the other?
Can this be determined or is it experimental?