General Biology: Organic Molecules, Isomerism, and Functional Groups

Which element is the backbone of organic molecules due to its ability to form four covalent bonds and create complex structures?

Miller's classic experiment demonstrated that a discharge of sparks through a mixture of gases could result in the formation of a large variety of organic compounds. Miller did not use ________ as one of the gases in his experiment.

In an ethene ($\mathrm{C_2H_4}$) molecule, each carbon atom is bonded to ________ hydrogen atoms.