Lithium sulfide, $\text{Li}_2\text{S}$, is a crystalline solid with a melting point of $938\degree\text{C}$. It conducts electricity when molten. Give the formulae of the particles found in solid lithium sulfide.
Explain, using the structure of the crystalline solid, why lithium sulfide has a high melting point.
Carbon monoxide, $\text{CO}$, is a gas at room temperature and pressure. It contains a coordinate bond. Explain what is meant by coordinate bond.
Draw a ‘dot-and-cross’ diagram to show the outer electrons in $\text{CO}$. Use $\times$ for the electrons from the C atom and $\bullet$ for the electrons from the O atom.
State two assumptions that are made about the behaviour of particles in an ideal gas.
Explain why $\text{N}_2$ does not behave as an ideal gas at very high pressures.
Complete the table by naming every type of intermolecular force (van der Waals’) in separate samples of $\text{N}_2(g)$ and $\text{CO}(g)$.
Suggest why the bond in a molecule of CO has a dipole moment.