Final answer:
Phosphorus is the element required for the building of molecules of ATP and DNA.
Step-by-step explanation:
The element required for the building of molecules of ATP and DNA is phosphorus. ATP (adenosine triphosphate) is a molecule that stores and transfers energy within cells. It consists of a nucleotide (adenine), a ribose sugar, and three phosphate groups. DNA (deoxyribonucleic acid) is a nucleic acid composed of nucleotides that contain a nitrogenous base (adenine, thymine, cytosine, or guanine), a deoxyribose sugar, and a phosphate group.