Among all the elements of the periodic system, a significant part belongs to those about which most people speak with fear. How else? After all, they are radioactive, which means a direct threat to human health.
Let's try to figure out exactly which elements are dangerous, and what they are, and also find out what their harmful effect on the human body is.
General concept of a group of radioactive elements
This group includes metals. There are a lot of them, they are located in the periodic system immediately after lead and to the very last cell. The main criterion by which it is customary to attribute an element to a group of radioactive ones is its ability to have a certain half-life.
In other words, radioactive decay is the transformation of a metal core into another, daughter, which is accompanied by the emission of a certain kind of radiation. In this case, some elements transform into others.
A radioactive metal is one in which at least one isotope is such. Even if there are six total varieties, and only one of them will be the carrier of this property, the whole element will be considered radioactive.
Types of radiation
The main options for radiation that is emitted by metals during decays are:
- alpha particles;
- beta particles or neutrino decay;
- isomeric transition (gamma rays).
There are two options for the existence of such elements. The first is natural, that is, when a radioactive metal is found in nature and in the simplest way, under the influence of external forces, over time is converted into other forms (manifests its radioactivity and decays).
The second group is metals artificially created by scientists, capable of rapid decay and powerful release of a large amount of radiation. This is done for use in certain fields of activity. Installations in which nuclear reactions are carried out by converting one element to another are called synchrophasotrons.
The difference between the two indicated methods of half-life is obvious: in both cases it is spontaneous, but only artificially produced metals give exactly nuclear reactions in the process of destructuring.
Basics of the designation of such atoms
Since for most of the elements only one or two isotopes are radioactive, it is customary to indicate the specific form in the notation, and not the entire element as a whole. For example, lead is just a substance. If we take into account that it is a radioactive metal, then we should call it, for example, “lead-207”.
The half-lives of the particles in question can vary greatly. There are isotopes that exist for only 0.032 seconds. But along with them there are also those that decay millions of years in the bowels of the earth.
Radioactive Metals: List
A complete list of all the elements belonging to the group under consideration can be quite impressive, because in all about 80 metals belong to it. First of all, these are all standing in the periodic system after lead, including a group of lanthanides and actinides. That is, bismuth, polonium, astatine, radon, France, radium, Rutherfordium and so on according to serial numbers.
Above the designated border there are many representatives, each of which also has isotopes. However, some of them may be just radioactive. Therefore, it is important which species the chemical element has. Almost every representative of the table has a radioactive metal, or rather one of its isotopic varieties. For example, they have:
- calcium;
- selenium;
- hafnium;
- tungsten;
- osmium;
- bismuth;
- indium;
- potassium;
- rubidium;
- zirconium;
- europium;
- radium and others.
Thus, it is obvious that there are a lot of elements showing the properties of radioactivity - the vast majority. Some of them are safe due to too long half-lives and are found in nature, while the other is artificially created by man for various needs in science and technology and is extremely dangerous for the human body.
Characteristics of Radium
The name of the element was given by its discoverers - the spouses Curie, Pierre and Maria. It was these people who first discovered that one of the isotopes of this metal - radium-226 - is the most stable form that has special properties of radioactivity. This happened in 1898, and a similar phenomenon only became known. A detailed study of it was precisely what the chemists' spouses took up.
The etymology of the word takes its roots from the French language, in which it sounds like radium. In total, 14 isotopic modifications of this element are known. But the most stable forms with mass numbers are:
Form 226 has a pronounced radioactivity. Radium itself is a chemical element at number 88. The atomic mass [226]. As a simple substance capable of subsistence. It is a silver-white radioactive metal with a melting point of about 670 0 C.
From a chemical point of view, it exhibits a fairly high degree of activity and is able to react with:
- water
- organic acids, forming stable complexes;
- oxygen forming an oxide.
Properties and Application
Radium is also a chemical element that forms a series of salts. Its nitrides, chlorides, sulfates, nitrates, carbonates, phosphates, chromates are known. There are also double salts with tungsten and beryllium.
The fact that radium-226 can be hazardous to health, its discoverer Pierre Curie did not immediately recognize. However, he managed to verify this when he conducted the experiment: for a day he walked with a test tube with metal tied to the shoulder of his hand. An unhealing ulcer appeared at the place of contact with the skin, which the scientist could not get rid of for more than two months. The spouses did not abandon their experiments on the phenomenon of radioactivity, therefore both died from a large dose of radiation.
In addition to the negative value, there are a number of areas in which radium-226 is used and benefits:
- Indicator of displacement of the ocean waters.
- Used to determine the amount of uranium in a rock.
- Included in lighting mixtures.
- In medicine, it is used to form therapeutic radon baths.
- Applied to remove electrical charges.
- With its help, defectoscopy of casting is carried out and seams of parts are welded.
Plutonium and its isotopes
This element was discovered in the forties of the XX century by American scientists. It was first isolated from uranium ore, in which it was formed from neptunium. The latter is the result of the decay of the uranium core. That is, all of them are closely interconnected by common radioactive transformations.
There are several stable isotopes of this metal. However, the most common and practically important variety is plutonium-239. Known chemical reactions of this metal with:
- oxygen
- acids;
- water
- alkalis;
- halogens.
According to its physical properties, plutonium-239 is a brittle metal with a melting point of 640 0 C. The main ways of influencing the body are the gradual formation of oncological diseases, the accumulation of bones in the bones and their destruction, lung diseases.
The area of use is mainly the nuclear industry. It is known that when one gram of plutonium-239 decays, such an amount of heat is released that is comparable to 4 tons of burned coal. That is why this type of metal finds such wide application in reactions. Nuclear plutonium is a source of energy in nuclear reactors and thermonuclear bombs. It is also used in the manufacture of electric energy batteries, the service life of which can reach five years.
Uranium - a source of radiation
This element was discovered in 1789 by a chemist from Germany Klaprot. However, people managed to study its properties and learn how to put them into practice only in the 20th century. The main distinguishing feature is that radioactive uranium is capable of forming nuclei during natural decay:
- lead 206;
- krypton;
- plutonium-239;
- lead 207;
- xenon.
In nature, this metal is light gray in color, has a melting point above 1100 0 C. It is found in minerals:
- Uranium Mica.
- Uraninite.
- Nasturan.
- Otenitis.
- Tyuyunmunit.
Three stable natural isotopes and 11 artificially synthesized are known, with mass numbers from 227 to 240.
Radioactive uranium is widely used in industry, capable of rapidly decaying with the release of energy. So, it is used:
- in geochemistry;
- mining;
- nuclear reactors;
- in the manufacture of nuclear weapons.
The effect on the human body is no different from the previous metals examined - accumulation leads to an increased dose of radiation and the occurrence of cancerous tumors.
Transuranic elements
The most important of the metals following uranium in the periodic system are those that were discovered recently. Literally in 2004, sources were published confirming the birth of 115 elements of the periodic system.
It became the most radioactive metal of all known to date - ununpentium (Uup). Its properties remain unstudied so far, because the half-life is 0.032 seconds! It is simply impossible to consider and reveal details of the structure and manifest features under such conditions.
However, its radioactivity is many times higher than that of the second element in this property - plutonium. Nevertheless, it is not ununpentium that is used in practice, but its slower comrades in the table - uranium, plutonium, neptunium, polonium, and others.
Another element - unbibium - theoretically exists, but practically scientists of different countries cannot prove this since 1974. The last attempt was made in 2005, but was not confirmed by the general council of chemical scientists.
Thorium
It was discovered back in the 19th century by Berzelius and named after the Scandinavian god Thor. It is a weakly radioactive metal. Five of its 11 isotopes have this feature.
The main use in nuclear power is not based on the ability to emit a huge amount of thermal energy during decay. The peculiarity is that thorium nuclei are able to capture neutrons and turn into uranium-238 and plutonium-239, which already enter directly into nuclear reactions. Therefore, thorium can also be attributed to the group of metals under consideration.
Polonium
Silver-white radioactive metal at number 84 in the periodic system. It was discovered by the same ardent researchers of radioactivity and everything connected with it, by the spouses Maria and Pierre Curie in 1898. The main feature of this substance is that it freely exists for about 138.5 days. That is, this is the half-life of this metal.
It is found in nature as part of uranium and other ores. It is used as a source of energy, and quite powerful. It is a strategic metal, as it is used for the manufacture of nuclear weapons. The number is strictly limited and is under the control of each state.
It is also used to ionize air, eliminate static electricity in the room, in the manufacture of space heaters and other similar items.
Effects on the human body
All radioactive metals have the ability to penetrate the skin of a person and accumulate inside the body. They are very poorly excreted with waste products, generally not excreted with sweat.
Over time, they begin to affect the respiratory, circulatory, nervous systems, causing irreversible changes in them. Affect cells, causing them to function abnormally. As a result, the formation of malignant tumors occurs, oncological diseases occur.
Therefore, each radioactive metal is a great danger to humans, especially if we talk about them in their pure form. Do not touch them with unprotected hands and be in the room with them without special protective equipment.