Answer
Carbon is central to the diversity of organic molecules due to its unique ability to form four covalent bonds with other atoms or functional groups. As different molecules attach to a carbon molecule, it consequently alters its shape as well as its chemical properties. With this, several molecules with different properties can be formed (i.e. polymers).
Work Step by Step
Since carbon is able to share four electrons on its outer shell, it can form four covalent bonds with other molecules such as other fellow carbon atoms or functional groups. Each group attached to the central carbon atom will then alter the overall shape of the molecule and affect its properties just like how the number of groups attached to the central carbon atom affects molecular structure. As these monomers bond and form longer chains, they form new shapes and possess new properties.
