Half-life period radium

The gases except radon occur as minor constituents in the atmosphere. Radon is obtained as a product of disintegration from radium and is radioactive. The most stable isotope Rn is a short lived isotope with a half life period of 3.8 days. Table 2.1 gives the percentage by volume of the noble gases in the atmosphere. 

The half-life period for the decomposition of radium is 1600 years (5,04 xlO a). Calculate the rate constant in min" and sec, assuming that the reaction is first-order. In how many years will 90 percent of a given amount of radium disappear ... 

Ra.don Sepa.ra.tion, Owing to its short half-life, radon is normally prepared close to the point of use in laboratory-scale apparatus. Radium salts are dissolved in water and the evolved gases periodically collected. The gas that contains radon, hydrogen, and oxygen is cooled to condense the radon, and the gaseous hydrogen and oxygen are pumped away. 

Radium is chemically similar to barium it displays a characteristic optical spectrum its salts exhibit phosphorescence in the dark, a continual evolution of heat taking place sufficient in amount to raise the temperature of 100 times its own weight of water 1°C every hour and many remarkable physical and physiological changes have been produced. Radium shows radioactivity a million times greater than an equal weight of uranium and. unlike polonium, suffers no measurable loss of radioactivity over a short period of time (its half life is 1620 years). From solutions of radium salts, there is separable a radioactive gas radium emanation, radon, which is a chemically ineit gas similai to xenon and disintegrates with a half life of 3.82 days, with the simultaneous formation of another radioactive element, Radium A (polonium-218). 

Only radium-226 has any commercial applications. It has a half life of 1,620 years. After that period of time, only half of the original sample... 

It is customary to express the stability of a radioelement in terms of its half-life, by which is meant the time that would be required for one half of a given mass of the element to undergo natural disintegration. Thus the period of half-life or half-change of radium is 1600 years. If therefore we have to-day a gram of radium, in 1600 years there will be only half a gram left, and in a further 1600 years the amount will have fallen to 0-25 gm. and so on. 

Such systems are called radioisotope generators. Rn is sometimes used for the radiotherapeutic treatment of cancer. This product is isolated by separating it as a gas from the parent substance Ra which is normally in the form of solid or a solution of RaBr2. Rn grows into the radium sample with a half-life of 3.8 d. After a 2-week period, following a separation of radon from radiiun, approximately 90% of the maximum amount of radon has grown back in the radium sample. Consequently, it is useful to separate Rn each 2 weeks from the radium samples since further time provides very little additional radioactivity. The Rn is an a emitter the ther utic value comes from the irradiation of the tissue by the y-rays of the decay daughters Pb and Bi which reach radioactive uilibrium extremely rapidly with the Rn. 

In 1898, in Cambridge, England, a New Zealander, Ernest Rutherford, demonstrated that there were at least two different types of radiation with different penetrating power. He called these alpha and beta radiation. He subsequentiy worked at McGill University in Montreal, Canada, and found more radioactive elements different types of radium and thorium, and actinium. He proposed that these were links in chains of radioactive materials, called the transformation theory. Rutherford and his colleague, Frederic Soddy, described that the rate of decay of radioactive elements were characteristic of the element, and came to be known as half-life. Decay follows the law of probability. Over a given period of time, each atom has a certain probability of decaying, a process that results from the random movements of the subatomic components of the radioactive atoms. This was the first instance in physics of a truly unpredictable phenomenon. The decay of a radioactive atom was probabilistic. 

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