Half-life period uranium

Until vciy recently only ninety-two elements were recognized and the periodic classification ended with the element uranium. In 1940 McMii.i.an and Abelson showed that bombardment of uranium witli neutrons led to the production of an isotope of a new clement, neptunium, of atomic number 93. Diis isotope whu h has a half life period of 2 3 days,... 

Harkins2 points out that of the known elements bismuth has the highest odd atomic number (83) except the radioactive descendants of uranium or thorium, whose half life periods, so far as they are known, are very short. The even atomic numbers from 82 to 92 are represented fully and many of these elements are very stable. It seems reasonable, therefore, to conclude that the electron systems required for the atomic numbers 85 and 87 are unstable and may not be able to exist at all. 

The position is even worse with uranium, U(238), the half-life period of which is 4,500 million years. During that period a gram of the metal would, it is true, evolve an enormous amount of energy, equivalent to 3 x io12 gm-calories. This could raise 30,000 tons of water from freezing to boiling point, or afford hot baths for more than one million people — a matter of supreme indifference to those politicians who do not bathe. 

Actinium is a member of a third radioactive seres, known as the actinium series, which originates in actino-uranium, an isotope of uranium I with a half-life period of 4 X io8 years. It occurs in all uranium minerals in a constant ratio to UI whatever the age. 

Neptunium - the atomic niunber is 93 and the chemical symbol is Np. The name derives from the planet Neptune (the Roman god of the sea), since it is the next outer-most planet beyond the planet uranus in the solar system and this element is the next one beyond uranium in the periodic table.lt was first synthesized by Edwin M. McMillan and Philip H. Abelson in 1940 via the nuclear reaction n, y) U P = p. The longest half-life associated with this mistable... 

Actinium is the last (bottom) member of group 3 (IIIB) of elements in the periodic table and the first of the actinide series of metallic elements that share similar chemical and physical characteristics. Actinium is also closely related in its characteristics to the element lanthanum, which is located just above it in group 3. The elements in this series range from atomic number 89 (actinium) through 103 (lawrencium). Actiniums most stable isotope is actinium-227, with a half-life of about 22 years. It decays into Fr-223 by alpha decay and Th-227 through beta decay, and both of these isotopes are decay products from uranium-235. 

Plutonium has a short half-life (24,360 years), so any plutonium initially in Earth s crust has long since decayed. The same is true for any heavier elements with even shorter half-lives from which plutonium might originate. Trace amounts of plutonium can occur naturally in U-238 concentrations, however, as a result of neutron capture, where U-238 becomes U-239 and after beta emission becomes Np-239 and after further beta emission becomes Pu-239. (There are elements in Earth s crust with half-lives even shorter than plutonium s, but these are the products of uranium decay—between uranium and lead in the periodic table of elements.)... 

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). 

Trace quantities of uranium in aluminum were determined by Mackintosh and Jervis (55). Two methods were described, one utilizing fission product barium while the other used the reaction U (n,7)U , half-life 23.5 min. In the latter case, after simple chemistry, uranium was mounted as the diuranate. Fairly good agreement was obtained between the two methods, that using U being the more sensitive and requiring shorter irradiation periods. 

According to this equation, the number of Th atoms, N2, increases with time with the half-life of Th. In other words, after a period of 24.1 d there is 50% of the maximum value of Th, after 48.2 d there is 75% of the final maximum value, etc. This is illustrated by the change in the uranium fraction activity in Figure 1.1. Further, from the relationship (4.55) we can see that the maximum value of thorium (r = 00) is giv by... 

As decay occurs, the remaining activity declines. The time it takes for a radionuclide to lose half its activity is its half-life (ti/2), which may range from extremely short to extremely long periods. The half-lives of polonium-214 and uranium-238, for example, are 163.7ps and 4.46x10 years, respectively. As individual isotopes decay they can form new stable or unstable isotopes in a series of steps that eventually ends in a stable nucleus. The type of decay and the half-lives of the intermediaries in a decay series is characteristic of the isotope e.g., radioactive thorium-232 undergoes the following decay steps to result in a stable isotope of lead ... 

As for uranium itself, that has a half-life of 4,500,000,000 years. This is a tremendous period of time, and in all the history of the earth, only a fraction of the original supply of uranium has had a chance to break down. Thorium breaks down even more slowly, its half-life being 14,000,000,000 years. 

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