Figure 15-3 Noncarbon Organic Molecules? When any element other than carbon that can make three or more covalent bonds combines, it makes compounds that are too soft, too hard, too reactive, or too inert to be useful in supporting life. Consider silicon. (a) The silicon-oxygen pair that creates the backbone of silicone is too inert to allow such molecules to react rapidly and thereby serve as organic molecules. Furthermore, these bonds produce gel or liquid compounds, as shown. (b) When the backbone is silicon-oxygen-oxygen, the bonds are rigid, as in this quartz rock.