Question

The melting point of lithium $\left(181^{\circ} C \right)$ is just double the melting point of sodium $\left(98^{\circ} C \right)$ because

• A. down the group, the hydration energy decreases
• B. down the group, the ionization energy decreases
• C. down the group the cohesive energy decreases
• D. None of these

Answer 1

Answer: (C)

The atom becomes larger on descending the group, so the bonds become weaker (metallic bond), the cohesive force/energy decreases and accordingly melting point also decreases.