Chapter 7, Problem 96A

Interpretation Introduction

Interpretation:

The large difference in the melting point of Beryllium which is 1287(C and Lithium which is 180(C needs to be explained.

Concept introduction:

Metallic bonds are those where the metal forms metal ions which are embedded in a sea of electrons. Its ionisation energy is low. Due to the presence of empty orbitals, the metal atoms overlap their valence orbitals and lose their valence electrons.

Answer to Problem 96A

The element Beryllium has higher melting point than Lithium as it has two delocalized electrons thus increasing the lattice energy and henceforth it smelting point.

Explanation of Solution

Metallic bonds are formed when metal ions are surrounded by sea of electrons. It occurs between two metals. Its ionisation energy is low. Due to the presence of empty orbitals, the metal atoms overlap their valence orbitals and lose their valence electrons.

Lithium belongs to group 1 and Beryllium belongs to group 2. Lithium has one valence electrons while Beryllium has two valence electrons.

In case of Lithium it indicates that this one electron is delocalized in the metallic lattice. Hence, the energy between this one electron and metal is lower.

In case of Beryllium, there are two outermost electrons and hence delocalizes two electrons in metallic lattice. Due to these two electrons the forces of attraction between delocalized electrons and metal ions are more.

Hence, with increased delocalized electrons, the lattice energy increases thereby increasing the melting point.

Conclusion

The element Beryllium has higher melting point than Lithium as it has two delocalized electrons thus increasing the lattice energy and henceforth its melting point.