How long does the radioactivity last?

How long does radioactivity last? After 1700 years, only half of the radium atoms would have disintegrated. This period of time is known as the half-life of radium. For some radioactive elements the half-life is a millionth of a second; for others, millions of years.

The nucleus of a heavy atom is made of many particles, held together by huge forces. But certain internal disturbance, or a hit by a particle from the outside, upsets the balance in the nucleus. That is when radioactivity occurs. Energy and mass fly of in the form of alpha and beta parti­cles, and gamma rays.

A new nucleus, belonging to a different element, is left behind. For example, the uranium atom disintegrates and changes to radium. Radium atoms in turn disintegrate into atoms of lead.

Most elements are not radioactive. The atoms of only, a few heavy elements are naturally radioactive. For example, the terrific explosion of nitroglycerin simply results in rearranging the atoms into new molecules. They form new compounds, but the atoms themselves remain unchanged. The inner part of the atom, the nucleus, has not been disturbed.

Until 1919 the nucleus seemed to be safe. But in that year Rutherford discovered how to get at it. By bombarding atoms with “bullets” he was able to hit the nucleus. His first success resulted in changing nitrogen atoms to oxygen atoms.

What happened in Rutherford’s experiment? A helium nucleus, travelling at high speed, struck a nitrogen nucleus and was absorbed into it. The resulting nucleus was unstable, and after pulsating a few times, broke up, threw off a hydrogen nucleus at high speed, and turned into oxygen.

Rutherford’s work was important in showing that man could attack the nucleus. But it was of no practical value. Although the hydrogen was shot out with more energy than the helium bullet had, there were so few hits that actually energy was lost in the process.

Notes:

disturbance ……... to occur ………… to fly off ……….. lead …………….. explosion ………. nitrogen ………… throw off ……….. bullet ……………

помеха, колебание случаться, происходить отлетать свинец взрыв азот извергать заряд

Plants and the atom

Scientists are studying the effects of atomic radiation on plants. Exposure to atomic radiation produces a num­ber of interesting changes in the structure and functions of plants and their offspring. The study of these changes is leading to a better understanding of the nature of plant life. Some of the discoveries may result in the development of better crop plants.

For many years, scientists have known which elements occur in plants and their proportion. But they were not cer­tain how the various elements entered the plant, nor did they understand the action of the elements within the plant.

Recently, however, plant scientists have learned to trace “tagged” atoms – radioactive isotopes which release small amounts of radiation – by the use of radiation detecting devices. When a few “tagged” atoms are mixed with normal ones, the movement of an element can be fol­lowed from the soil, through the plant, until it is stored in tissue or discharged from the plant. Atomic research al­ready has led to many advances in our knowledge of plant life. These discoveries have been put to many practical uses, including the improvement of fertilizing technique.

Notes:

exposure ……….. offspring ……….. crop plants ……... “tagged” atoms … tissue …………… fertilizing ……….

выставление под действие атмосферного влияния плод хлебные злаки меченые атомы биол. ткань удобрение