The actinides or actinoids are the chemical elements with atomic numbers between 90 and 109 inclusively. They occur between Groups 4 and 5 in Period 7 regarding the periodic table. All elements in this family are radioactive. 5 actinides namely: thorium, protoactinium, uranium, neptunium, and plutonium have been located in nature. The other actinides have been produced artificially in nuclear reactors or particle accelerators.
For many years, the list of chemical elements known to scientists ended with atomic no. Scientists were uncertain as to whether elements heavier than uranium should ever be found. Then, in 1940, a remarkable discovery atom structure University of California physicists Edwin McMillan and Philip Abelson were studying nuclear fission. During their research, the duo located evidence for the existence of an unique element with atomic no. 94, 3 greater than that of uranium.
This new element was first transuranium heaver than uranium element ever discovered. McMillan and Abelson named it neptunium, subsequent to the planet Neptune, just as uranium had been named subsequent to the planet Uranus. Later within similar year, McMillan and his 3 other colleagues located a 2nd transuranium element, which they named plutonium, subsequent to the planet Pluto. At that point, the race was on to develop more synthetic transuranium elements, but the studies process was not easy. The approach was to fire subatomic particles or tiny atoms, like those of helium, at a very large nucleus by means of a particle accelerator.
If the smaller particle should be created to merge with the larger nucleus, an unique atom should be produced. Over time, techniques became more and more sophisticated, and ever-heavier elements were created: americium no. 96 in 1944; berkelium no. 97 in 1949; californium no. 98 in 1950; einsteinium no.
100 in 1952; mendelevium no. 101 in 1955; nobelium no. 102 in 1958; and lawrencium no. Studies regarding the actinide elements are between the highest many ingenious in all of chemistry. In some cases, no higher than one or 3 atoms of an unique element have been produced.
Yet scientists have been can learn those little atoms well enough to discover simple properties regarding the elements. These studies are created even more difficult due to the fact that most actinide isotopes decay quickly, with half-lives of only a little days or a little minutes. With the discovery of lawrencium, the actinide family of elements is complete. Scientists have also located elements heavier than lawrencium, but these elements belong to lanthanide family or rare earth elements. Uranium is a dull gray metallic element, relatively abundant in Earth's crust, ranking no.
47 between the elements. Consequently perhaps not as well known, it is actually more abundant than more familiar elements for example tin, silver, mercury, and gold. By distant the highest many important property of uranium is its radioactivity. Natural uranium consists of 3 isotopes of mass numbers 234, 235, and 238. All 3 isotopes are radioactive.
Its most abundant isotope, uranium-238, decays by emitting an alpha particle with a half-life of 4. The half-life of uranium-238 is about equal to age of Earth. That means that about one-half of all the uranium located on Earth at its moment of creation is still here. The other one-half has decayed to other elements. Knowing the 1/2 life of uranium-238 scientists can estimate the age of rocks.
of uranium-238 located in any specific rock is compared to no. of daughter isotopes located with it. A daughter isotope is an isotope formed when some parent isotope, for example uranium-238, decays. The more daughter isotope present in a sample, the older the rock; the fewer daughter isotope, the younger the rock. The 2nd most abundant isotope of uranium, uranium-235, has the rare property of being fissionable, meaning that its atomic nuclei shall break apart when bombarded by neutrons.
The fission of a uranium-235 nucleus releases very large amounts of energy, more neutrons, and 3 large fission products. The fission products are the atomic nuclei formed when a fissionable nucleus for example uranium-235 breaks apart. The fission of uranium-235 nuclei has grow to extremely important within the manufacture of nuclear weapons and within the procedure of nuclear force plants. In fact, these applications account for the primary applications of uranium in everyday life. Thorium is a soft metal with a bright silvery luster when freshly cut.
It is relatively soft, with hardness about equal to that of lead. It is even more abundant than uranium, ranking no. 39 in abundance between the elements in Earth's crust. No higher than a little hundred tons of thorium is produced annually. About one-half of this production goes to manufacture of gas mantles, insulated chambers in which fuel is burned.
The rest goes for use as nuclear fuel, in sunlamps, in photoelectric cells or light sensitive cathode, and within the production of other alloys. At one time, the actinides other than uranium were no higher than scientific curiosities. They were fascinating topics of studies for scientists but of little practical interest. That situation has now changed, and all regarding the actinides that shall be prepared in large enough quantities have located some use or another. Plutonium, for example, is used within the manufacture of nuclear weapons and as the force source in nuclear force plants.
On a smaller scale, it shall also be used like a force source in smaller devices for example the heart pacemaker. Californium is used in smoke detectors, curium is a force source in space vehicles, and americium is utilized within the treatment of cancer. Most regarding the actinides are trans-uranium. They not ever occur free in nature. These metals are similar due to the fact that their atomic structures are similar; all shape compounds with the highest many common oxidation state 3.
They can be metals, with high luster and electrical conductivity and locate uses in petroleum and electronics industries, manufacture of super conductors, permanent magnets, ceramics, glass, and metal alloys. Radioactive elements hold very many of important uses and they also cause some dangerous problems if they can be not handled properly. Henri Becquerel first located out about radioactive elements late within the 19th century by placing some photographic film below uranium salts. The film was in a light-tight envelope, and it was exposed where he place the uranium on it. This behavior was eventually located to be caused by the emission of radiation from the decaying uranium which penetrated the cardboard envelope and exposed the film.
Ever since then, more elements have been investigated for their radioactivity, and different isotopes of elements have different radioactive behavior. Many are used commercially and medically, and others are just nuisances. Tiny amounts of radioactive fabrics shall be ingested as radiotracers to look how sure chemicals are taken up by the body. If a well-being researcher is interested in how a sure element is distributed by the body subsequent to it is ingested, he can decide to use a radioactive isotope of an usual element, combine it in, and then use sensitive radiation detectors to look where it ends up within the body. These are often used in studies to look how medications are absorbed and transported within the body.
Thorium, a naturally occurring radioactive element, is used in creating mantles for gas and kerosene lamps due to the fact that thorium oxide glows brightly when heated. The radioactive elements uranium and plutonium are used within the generation of electricity in nuclear force plants. Tiny radioactive sources of particles are used in many home smoke detectors. These elements are also used within the production of nuclear weapons. One can propose that the presence of nuclear weapons has prevented war, but also that they have created the consequences of likely war many worse than before.
Depleted uranium, that is, naturally occurring uranium with the U235 taken out, is mostly U-238, that is a bit fewer radioactive than the natural material. This fabric is very dense and hard, however, and otherwise useless, so the army uses it to make bullets and other shells. These can pierce steel armor. Whether this is a good use or an evil use depends on which side regarding the gun one is standing on. Some radioactive elements glow due to the fact that of their radioactive decays.
They emit electrons or alpha particles, changing from one kind of element to another, and as the electrons within the atoms rearrange themselves to new atom's configuration, they emit light. Radium was used for watch dials due to the fact that it glows green. Tritium should possibly be used like a backlight in watches due to the fact that it too glows green. Tritium is still used in tiny quantities in tiny vials on watch hands and to mark the hour positions on watch dials. Radium isn't used anymore, however.
Radiation, even in tiny doses, can cause cancer in humans and other living things. Fast moving photons gamma rays, electrons beta rays and helium nuclei alpha particles can crash into other molecules and change their structure. If this happens to a DNA molecule, it can damage the genetic information, and sometimes turn a cell cancerous. Radiation also causes burns, many like sunburn, in large doses over brief amounts of time. Usually we can walk distant from radioactive substances, lowering our risk.
But if we ingest radioactive elements, they wait with us. Particularly nasty radioactive elements with radon and radioactive iodine. Radon is a chemically inert gas with a brief half-life and that is why decays rapidly, emitting radiation faster than other elements. It is produced naturally like a decay product of longer-lived radioactive elements in rock and soil. It shall diffuse through basement walls and into people's homes.
It increases the rate of lung cancer when people breathe it in. It is a good plan to ventilate basements and have them checked, particularly in parts regarding the region where radon is common. Radioactive iodine shall also be readily absorbed by the body and becomes incorporated in bones, and is that is why difficult to eliminate from the body. The radiation it emits can cause bone cancer over long periods of time. The radium on watch dials was incorporated in paint.
Workers used to paint the watch dials by hand, and some should even lick their paint brushes to make a sharper tip. They ingested radon paint, and some became ill with cancer. Naturally occurring uranium also was used to make bright yellow paint, but now this too was stopped. Some people complain about radiation emitted by those depleted-uranium bullets and shells left over in wars. Residents of parts where such munitions have been used are concerned related to the long-term well-being effects regarding the radioactivity.
There is some concern that the primary dangers from the leftover uranium powder should be due to chemical poisoning rather than radiation. Plutonium, while radioactive, also happens to be just plain poisonous. Person bodies don't ever deal well with heavy metals: lead, mercury, and arsenic return to mind as things not to ingest due to the fact that they can be poisonous. Plutonium shall well be the highest many poisonous regarding the lot.
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