A single heteroatom, for example, $\ce{–Cl}$ and $\ce{=O}$; a heteroatom bearing one or more hydrogen atoms or other heteroatoms, for example, $\ce{–NH2}$, $\ce{–OH}$, $\ce{–SO3H}$, $\ce{–PO3H2}$ and $\ce{-IO2}$; or a heteroatomic group attached to or containing a single carbon atom, for example, $\ce{–CHO}$, $\ce{–C#N}$, $\ce{–COOH}$ and $\ce{–NCO}$, attached to a parent hydride.