The 4n+2 chain of U-238 is commonly called the Radium Series (sometimes Uranium Series). Beginning with naturally occurring uranium-238, this series includes the following elements: astatine, bismuth, lead, polonium, protactinium, radium, radon, thallium and thorium. All are present, at least transiently, in any natural uranium-containing sample, whether metal, compound, or mineral. The series terminates with lead-206.
The details in decay chain (symbol, atomic mass, number of protons, half-life, decay children) are taken from contributor .
Caption: Nuclear decay chain, radium series. Diagram of the nuclear decay chain of uranium-238 (U-238) with isotopes (shown by chemical symbols) plotted by mass number (A) against atomic number (Z). Isotopes are colour-coded by their primary decay route (purple, red arrows: alpha decay; blue, blue arrows: beta decay). Decays are rare (dotted lines) or dominant (solid lines). The dominant route (yellow) ends with the stable (green) lead-206 (Pb-206). Other elements in this natural decay chain are: protactinium (Pa), thorium (Th), radium (Ra), radon (Rn), astatine (At), polonium (Po), bismuth (Bi), thallium (Tl), and mercury (Hg).
a group of genetically related radioisotopes in which each succeeding isotope is formed as a result of the alpha or beta decay of the preceding isotope. Each radioactive series has a parent isotope, which is the one with the longest half-life. Radioactive series end in stable isotopes.
The thorium, actinouranium, and uranium-radium series (natural radioactive series) exist in nature. The reason for this is that the half-lives of 232Th (1.41 × 1010 yr), 235U (7.13 × 108 yr), and 238U (4.51 × 109 yr) are comparable to the age of the earth (several billion years) and that these isotopes have not entirely decayed. These natural radioactive series end with the isotopes of lead 208Pb, 207Pb, and 206Pb.
Radium is the heaviest and most reactive element of the alkaline earth metals family. Radium is rare because of its high reactivity and short half-life. It is a part of the group of elements that appears after bismuth (Z=83) which are all radioactive and unstable. As Uranium decays it briefly turns into radium and eventually turns into stable lead.