Which of the following has minimum lattice energy $:-$

Covalent compounds have low melting points because:

Draw the structure of
$(i)$ $BeCl_2$ (vapour)
$(ii)$ $BeCl_2$ (solid).

The lattice enthalpy of an ionic compound is the enthalpy change when one mole of an ionic compound in its solid state dissociates into its ions in the gaseous state. It is impossible to determine it directly by experiment. Suggest and explain an indirect method to measure the lattice enthalpy of $NaCl_{(s)}$.

Give reasons: Graphite is used as a lubricant.

Graphite is a soft solid lubricant extremely difficult to melt. The reason for this anomalous behaviour is that graphite