The discovery of the structure of the atomic nucleus was one of the most important stages in the development of modern physical knowledge. Scientists came to the right conclusions about the structure of the smallest particles not immediately. And much later, other laws were discovered - for example, the laws of motion of microparticles, as well as the features of the transformation of atomic nuclei that occur during radioactive decay.
Rutherford's experiences
For the first time, the radioactive transformations of atomic nuclei were studied by the English researcher Rutherford. Even then, it was clear that the bulk of the atom falls on its core, since electrons are many hundreds of times lighter than nucleons. In order to investigate the positive charge inside the nucleus, in 1906, Rutherford proposed exploring the atom by probing with alpha particles. Such particles arose during the decay of radium, as well as some other substances. In the course of his experiments, Rutherford received an idea of the structure of the atom, which was given the name "planetary model."
The first observations of radioactivity
Back in 1985, the English researcher W. Ramsay, who is known for his discovery of argon gas, made an interesting discovery. He discovered helium gas in a mineral called cleveite. Subsequently, a large amount of helium was also found in other minerals, but only in those containing thorium and uranium.
To the researcher this seemed very strange: where could the gas come from in minerals? But when Rutherford began to study the nature of radioactivity, it turned out that helium is a product of radioactive decay. Some chemical elements “generate” others, with completely new properties. And this fact contradicted all the previous experience of chemists of that time.
The observation of Frederick Soddy
Together with Rutherford, the scientist Frederick Soddy was directly involved in the research. He was a chemist, and therefore all his work was carried out in relation to the identification of chemical elements according to their properties. In fact, the radioactive transformations of atomic nuclei were first noticed by Soddy. He managed to find out what alpha particles are, which Rutherford used in his experiments. After making measurements, scientists found that the mass of one alpha particle is 4 atomic units of mass. Having accumulated a certain amount of such alpha particles, the researchers found that they turned into a new substance - helium. The properties of this gas were well known to Soddy. Therefore, he argued that alpha particles were able to capture electrons from the outside and turn into neutral helium atoms.
Changes inside the nucleus
Subsequent studies were aimed at identifying the features of the atomic nucleus. Scientists realized that all transformations do not occur with electrons or the electron shell, but directly with the nuclei themselves. It was the radioactive transformations of atomic nuclei that contributed to the conversion of some substances into others. Then even the features of these transformations were unknown to scientists. But one thing was clear: as a result of them, new chemical elements somehow appear.
For the first time, scientists managed to trace such a chain of metamorphoses in the process of converting radium to radon. Researchers, as a result of which such transformations occurred, accompanied by special radiation, the researchers called nuclear. After making sure that all these processes occur precisely inside the nucleus of the atom, scientists began to study other substances, not only radium.
Open types of radiation
The main discipline that may require answers to such questions is physics (Grade 9). The radioactive transformations of atomic nuclei are included in its course. Carrying out experiments on the penetrating power of uranium radiation, Rutherford discovered two types of radiation, or radioactive transformations. The less penetrating type was called alpha radiation. Beta radiation was later investigated. Gamma radiation was first studied by Paul Willard in 1900. Scientists have shown that the phenomenon of radioactivity is associated with the decay of atomic nuclei. Thus, according to the prevailing notions of the atom as an indivisible particle, a crushing blow was dealt.
Radioactive transformations of atomic nuclei: main types
It is now believed that during radioactive decay there are three types of transformations: alpha decay, beta decay, electronic capture, otherwise called K-capture. In alpha decay, an alpha particle is emitted from the nucleus, which is the nucleus of a helium atom. The radioactive nucleus itself in this case turns into one that has a lower electric charge. Alpha decay is characteristic of substances that occupy the last places in the periodic table. Beta decay also enters into the radioactive transformations of atomic nuclei. The composition of the atomic nucleus with this type also changes: it loses neutrinos or antineutrinos, as well as electrons and positrons.
This type of decay is accompanied by short-wave electromagnetic radiation. In electron capture, the atomic nucleus absorbs one of the nearest electrons. In this case, the beryllium core can turn into a lithium core. This type was discovered in 1938 by a physicist from America named Alvarez, who also studied the radioactive transformations of atomic nuclei. The photos in which the researchers tried to capture such processes contain images that look like a blurry cloud, due to the small sizes of the particles being studied.