Decay of thorium

Self-Test 17.1B Identify the nuclide produced by (a) a decay of thorium-232, (b) (3 decay of radium-228. 

The rate constant for the radioactive decay of thorium-232 is 5.0 X 10 u/year. Determine the half-life of thorium-232. 

While studying radium, Friedrich Ernst Dorn (1848—1916) found that it gave off a radioactive gas that, when studied in more detail, proved to be the sixth noble gas. Dorn was given credit for its discovery in 1900. He called it radon, a variation of the word radium. Sir Wdham Ramsay and R. W. Whytlaw-Gray, who also investigated the properties of radon, called it niton from the Latin word nitens, which means shining. Several other scientists who worked with radon named it thoron because of the transmutation of radon-220 from the decay of thorium. However, since 1923, the gas has been known as radon because it is the radioactive decay gas of the element radium. The name is derived from the Latin word radius, which means ray. ... 

If an unstable nucleus emits an alpha particle, its atomic number decreases by 2 and its mass number decreases by 4. The decay of thorium-232 provides an example ... 

The thorium isotope-232 is not stable. It breaks down into two parts. This process of breaking down is called decay. The decay of thorium-232 produces a small part called "alpha" radiation and a large part called the decay product. The decay product of thorium-232 also is not stable. Like thorium-232,... 

When thorium emits alpha particles, it disintegrates into other daughter radionuclides (radioactive materials), such as radium-226 and radon-222 (from thorium-230 in the uranium-238 decay series) or radium-228 and thoron (radon-220 from thorium-232 in the thorium decay series). It eventually decays to stable lead-208 or -206, which is not radioactive. More information about the decay of thorium can be found in Chapter 3. The toxicological characteristics of radon, radium, and lead are the subject of separate ATSDR Toxicological profiles. 

What particle is produced by decay of thorium-214 to radium-210 ... 

The last of the family of the noble gases was found in 1900 by Owens and Rutherford. This was radon-220, a product of the Radioactive Decay of thorium. Also in the same year, radon-222, which is a product of the radioactive decay of radium, was discovered by Dorn. 

Using the information provided in Table 25-3, write a balanced nuclear equation for the alpha decay of thorium-230 ( Th). 

Plot the exponential decay curve for a period of five half-Uves for the decay of thorium-234 given in mJ Problem 80. How much time has elapsed when 30% of the original sample remains ... 

The isotope Th decays to ° Pb by the emission of six alpha particles, with a half-life of 1.39 X 10 ° years. Analysis of 1.00 kg of ocean sediment shows it to contain 7.4 mg of Th and 4.9 X 10 cm of gaseous helium at 0°C and atmospheric pressure. Estimate the age of the sediment, assuming no loss or gain of thorium or helium from the sediment since its formation and assuming that the helium arose entirely from the decay of thorium. 

Radon derives its name from the element radium. The gas is radioactive and is formed by radioactive decay processes deep in the earth. Uranium-238 decays very slowly to radium-226, which further decays by alpha particle emission to radon-222 (see Chapter 17). The half-life of radon-222 is 3.825 days. Other shorter-lived isotopes are formed from the decay of thorium-232 and uranium-235. Every square mile of soil to a depth of 6 inches is estimated to contain about 1 g of radium, which releases radon in tiny amounts into the atmosphere. 

There are essentially three sources of radioactive elements. Primordial nuclides are radioactive elements whose half-lives are comparable to the age of our solar system and were present at the formation of Earth. These nuclides are generally referred to as naturally occurring radioactivity and are derived from the radioactive decay of thorium and uranium. Cosmogenic nuclides are atoms that are constantly being synthesized from the bombardment of planetary surfaces by cosmic particles (primarily protons ejected from the Sun), and are also considered natural in their origin. The third source of radioactive nuclides is termed anthropogenic and results from human activity in the production of nuclear power, nuclear weapons, or through the use of particle accelerators. 

The radioactive decay of thorium-232 occurs in multiple steps, called a radioactive decay chain. The second product produced in this chain is actinium-228. Which of the following processes could lead to this product starting with thorium-232 ... 

Figure 16.4 The decay of thorium isotopes and the growth of daughters in separated thorium over a short time-scale (0.5 years)...

In the earth s crust thorium is almost four times more common than uranium, and the radioactive decay of thorium generates a considerable part of the geothermal energy. The primary source of thorium is monazite (Figure M25), a yellow or reddish-brown rare-earth phosphate. Seashore deposits at Travancore in India contain very big quantities of monazite. The mineral formula is (Ce,La,Nd,Th)PO and the thorium content in monazite ores is 5-10%. In 2001 the production of monazite concentrate in the world was 5710 tonnes [52.13], of which India accounted for 5000 toimes or 88%. Other producers were Brazil and Malaysia. 

Thorium is a naturally occurring radioactive element. Thorium-232 decays by emitting a single alpha particle to produce radium-228. Write the nuclear equation for this decay of thorium-232. 

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