- Radon is a chemical element; it has symbol Rn and atomic number 86. It is a radioactive noble gas and is colorless and odorless. Of the three naturally occurring radon isotopes, only 222Rn has a sufficiently long half-life (3.825 days) for it to be released from the soil and rock where it is generated. Radon isotopes are the immediate decay products of radium isotopes. The instability of 222Rn, its most stable isotope, makes radon one of the rarest elements. Radon will be present on Earth for several billion more years despite its short half-life, because it is constantly being produced as a step in the decay chains of 238U and 232Th, both of which are abundant radioactive nuclides with half-lives of at least several billion years. The decay of radon produces many other short-lived nuclides, known as “radon daughters”, ending at stable isotopes of lead. 222Rn occurs in significant quantities as a step in the normal radioactive decay chain of 238U, also known as the uranium series, which slowly decays into a variety of radioactive nuclides and eventually decays into stable 206Pb. 220Rn occurs in minute quantities as an intermediate step in the decay chain of 232Th, also known as the thorium series, which eventually decays into stable 208Pb.
- United States Department of the Treasury (Wikipedia)
The Department of the Treasury (USDT) is the national treasury and finance department of the federal government of the United States, where it serves as an executive department. The department oversees the Bureau of Engraving and Printing and the U.S. Mint. These two agencies are responsible for printing all paper currency and minting coins, while the treasury executes currency circulation in the domestic fiscal system. It collects all federal taxes through the Internal Revenue Service; manages U.S. government debt instruments; licenses and supervises banks and thrift institutions; and advises the legislative and executive branches on matters of fiscal policy. The department is administered by the secretary of the treasury, who is a member of the Cabinet. The treasurer of the United States has limited statutory duties, but advises the Secretary on various matters such as coinage and currency production. Signatures of both officials appear on all Federal Reserve notes.