21.   Every carbon atom and every hydrogen atom is the same.

22.   Exciting pictures show high-powered lasers blasting carbon atoms loose from targets.

23.   Forming the five other vertexes of each hexagon are five carbon atoms, each of which is bonded to either a hydrogen atom or a chlorine atom.

24.   He studied a catalyst that inserts two hydrogen atoms into a flat, two-dimensional molecule, between two carbon atoms.

25.   Methane is composed of four hydrogen atoms that surround a carbon atom.

26.   Nanotubes, those cylindrical molecules of carbon atoms, are steadily becoming much more than just a laboratory curiosity, as researchers develop potential applications for them.

27.   Nanotubes are structures only a handful of atoms across that form spontaneously from hexagonal arrays of carbon atoms.

28.   On the early Earth, ribose probably formed out of formaldehyde, which is a single carbon atom bonded to a water molecule.

29.   Patients drink a solution of urea that has been manufactured to contain carbon atoms that are heavier than normal.

30.   Plastics are made of an entwined mesh of long molecules called polymers, each with a central strand of carbon atoms.