Chlorine, $\text{Cl}_2$, is a gas at room temperature, but bromine, $\text{Br}_2$, is a liquid under the same conditions. Explain these observations.
The gases nitrogen, $\text{N}_2$, and carbon monoxide, $\text{CO}$, are isoelectronic, meaning that their molecules contain the same number of electrons. Suggest why $\text{N}_2$ has a lower boiling point than $\text{CO}$.
A ‘dot-and-cross’ diagram of a $\text{CO}$ molecule is shown. Only outer-shell electrons are included. In the table below, there are three copies of this structure. On the structures, draw a circle around a pair of electrons linked with each of the following: (i) a co-ordinate bond, (ii) a covalent bond, (iii) a lone pair.
Hydrogen cyanide, $\text{HCN}$, is a gas which is also isoelectronic with $\text{N}_2$ and with $\text{CO}$. Each molecule has a strong triple bond with the following bond energies: $\text{C} \equiv \text{N}$ in $\text{HCN}$ ($890\ \text{kJ mol}^{-1}$), $\text{N} \equiv \text{N}$ ($994\ \text{kJ mol}^{-1}$), $\text{C} \equiv \text{O}$ ($1078\ \text{kJ mol}^{-1}$). Even though each compound contains the same number of electrons and a strong triple bond in its molecule, $\text{CO}$ and $\text{HCN}$ are both very reactive whereas $\text{N}_2$ is not. Suggest a reason for this.
$\text{HCN}$ reacts with ethanal, $\text{CH}_3\text{CHO}$. Give the displayed formula for the organic product formed.
Identify the type of reaction.
Draw the mechanism for this reaction. You should include all full and partial charges and show the movement of electron pairs with curly arrows.