2. Complete the following Table \begin{tabular}{|c|c|c|} \hline Gas & Symbol & Colour* \\ \hline Oxygen & O2 & White \\ \hline Air & & \\ \hline Carbon Dioxide & & Brown and White \\ \hline & He & \\ \hline & NO & Black \\ \hline Nitrous Oxide & & \\ \hline & & Grey and White \\ \hline \end{tabular}