“There are as many atoms in one molecule of DNA as there are stars in a typical galaxy.”--Carl Sagan
But there are only 5 elements in DNA: P, C, N, O, and H.
Phosphorus is the most complex, with 15 protons, 15 electrons, and 16 neutrons. Twenty-three isotopes of phosphorus exist, with atomic weights ranging from 24 to 46, but all are radioactively unstable except 31P.