Dmitri Mendeleev published the periodic table of chemical elements in 1869 on the basis of emerging traits with some order as he placed the elements from the lightest to the most severe. When Mendeleev proposes his periodic table, he notes the gaps in the table and predicts that the unknown elements of the time exist with the proper traits to fill the void. He named them eka-aluminum, eka-boron and eka-silicon with atomic masses 44, 68 and 72 respectively.
Video Mendeleev's predicted elements
Prefiks
To give a temporary name to a predicted element, Mendeleev uses the eka prefix -, dvi -, and tri -, from the Sanskrit names digit 1 , 2, and 3, depending on whether the predicted element is one, two, or three places of the known element of the same group in the table. For example, germanium was called eka-silicon until its invention in 1886, and rhenium was called dvi-manganese before its invention in 1926.
The prefix eka - is used by other theorists, and not only in Mendeleev's own predictions. Prior to the invention, franium was referred to as cesium, and astatine as iodine. Sometimes, eka- is still used to refer to some transuranic elements, for example, eka-aktinium (or dvi-lanthanum ) for unbiunium. However the current official IUPAC practice is to use the name of a systematic element based on the atomic number of an element as a temporary name, rather than by its position in the periodic table as required by this prefix.
Maps Mendeleev's predicted elements
Original prediction
The four predicted elements are lighter than the rare-earth element, eka-boron ( Eb , Russia: ??????? ), eka-aluminum ( Ea or El , Russian: ????? ( Em ), and silicon ( Es /, Russian: ????????? ), proved to be a good predictor of the properties of scandium, gallium, technetium and germanium, which fill place in the periodic table assigned by Mendeleev. Early versions of the periodic table do not provide the rare elements now given to them, helping to explain why Mendeleev's prediction for heavier elements is unknown not as good as the lighter and why they are not so well known. or documented.
Scandium oxide was isolated at the end of 1879 by Lars Fredrick Nilson; Per Teodor Cleve acknowledged the correspondence and informed Mendeleev at the end of the year. Mendeleev had predicted an atomic mass of 44 for ekaboron in 1871, while scandium had an atomic mass of 44.955910.
In 1871 Mendeleev predicted the existence of an undiscovered element which he named eka-aluminum (due to its proximity to aluminum in the periodic table). The table below compares the quality of elements predicted by Mendeleev with actual gallium characteristics (discovered in 1875 by Paul Emile Lecoq de Boisbaudran).
Technetium was isolated by Carlo Perrier and Emilio SegrÃÆ'¨ in 1937, well after Mendeleev's lifetime, from a molybdenum sample that had been bombarded with a deuterium nucleus in a cyclotron by Ernest Lawrence. Mendeleev had predicted an atomic mass of 100 for the ecosystem in 1871, and the most stable technetium isotope was 98 Tc.
Germanium was isolated in 1886 and gives the best confirmation of the theory up to that point, as the contrast is more pronounced with its neighboring elements than the two previously confirmed predictions about Mendeleev doing with them.
Other predictions
The existence of elements between thorium and uranium was predicted by Mendeleev in 1871. In 1900 William Crookes isolated protactinium as a radioactive material from uranium, which he could not identify. Various protactinium isotopes were identified in Germany in 1913 and in 1918, but the name of protactinium was not given until 1948. Since thorium 1950, uranium and protactinium have been classified as actinides; then protactinium does not occupy the eka-tantalum place in what is now called Group 5. Eka-tantalum is actually a dubnium.
Mendeleev's 1869 had implicitly foretold the heavier analogue of titanium and zirconium, but in 1871 he placed the lanthanum there. The hafnium discovery of 1923 validated Mendeleev's original introduction in 1869.
Later prediction
In 1902, after receiving evidence for elements of helium and argon, Mendeleev placed this noble gas in Group 0 in its arrangement of the elements. Because Mendeleev doubts the atomic theory to explain the law of definite proportions, he has no reason to believe that hydrogen is the lightest element, and suggests that the lighter hypothetical member of Group 0 is chemically inert. elements may be undetectable and responsible for radioactivity. Currently some periodic table elements put a single neutron in this place, and it fits well with Mendeleev's prediction well.
Heavier than hypothetical proto-helium elements Mendeleev identified with coronium, named after the relationship with the unexplained spectral lines in the Sun's corona. The incorrect calibration provided a wavelength of 531.68 nm, which was eventually corrected to 530.3 Âμm, which Grotrian and EdlÃÆ' nà © n identified as coming from Fe XIV in 1939.
The lightest of the Group 0 gas, the first in the periodic table, was given the theoretical atomic mass between 5.3ÃÆ'â € "10 -11 and 9.6ÃÆ'â €" 10 -7 . The kinetic speed of this gas is calculated by Mendeleev to 2 500 000 meters per second. Almost no mass, these gases are assumed by Mendeleev to absorb all matter, rarely interact chemically. The high mobility and the very small mass of trans-hydrogen gases will result in a situation that they can be clarified, but it seems very dense.
Mendeleev later published the theoretical expression of ether in a small booklet entitled A Chemical Conception of the Ether (1904). Her 1904 publication once again contains two smaller and lighter atomic elements of hydrogen. He treats "ether gas" as an interstellar atmosphere consisting of at least two elements lighter than hydrogen. He claimed that these gases came from the hard internal bombardment of stars, the Sun being the most productive source of gas. According to Mendeleev's booklet, the interstellar atmosphere may consist of several additional elemental species.
Note
References
Further reading
- Scerri, Eric (2007). Periodic Table: The Story and Its Importance . New York: Oxford University Press. ISBN: 0-19-530573-6.
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