1. Study on the classification of elements before Mendeleev discovered the periodic law of elements.
(1) 1789, French chemist lavoisier listed the first Su Zhang Garden in the world in his monograph "Chemical Outline". He divided the known 33 elements into four categories: gas elements, nonmetals, metals and soil that can form salt. But he included some things, such as light, lime and magnesium oxide, as elements.
1. simple materials belongs to gaseous state and can be considered as elements: light, heat, oxygen, nitrogen and hydrogen.
2. Simple nonmetallic substances that can be oxidized into acids: sulfur, phosphorus, carbon, hydrochloric acid group, hydrofluoric acid group and boric acid group.
3. Simple metal substances that can be oxidized into salts: antimony, arsenic, silver, diamond, copper and tin. Iron, manganese, mercury, molybdenum, gold, platinum, lead, tungsten and zinc.
4. Simple soil capable of forming salt: lime, bitter soil, heavy soil, bauxite and silica.
(2) 1829, the German chemist J.W. 1780- 1849 studied the relationship between the atomic weight of elements and their chemical properties, and found that among the 54 known elements, there are 5 groups of similar elements, each group has 3 elements, which is called "three-element group". The atomic weight of one element in the middle of each group is the average of the other two elements. Such as lithium, sodium and potassium, the atomic weight of sodium is
(69+39. 1)/2=23。
③ In 1862, French geologist Chen courtois (A.E.B. 1820- 1886) drew a "spiral diagram". He arranged 62 known elements in the order of atomic weight into a spiral around a cylinder, and elements with similar properties appeared on a hard line. He was the first to point out the periodic changes in the properties of elements.
(4) 1863, the British chemist Newlands (Newlands, J.A.R. 1837- 1898) gave an octave. He periodically repeats known properties, and every eighth element is similar to the first element, just like the eighth note of octave in music has a similar repetition.
H 1 Li2 G3 Bo4 C5 N6 O7
F8 Na9 mg 10 al 1 1si 12p 13s 14
cl 15k 16 ca 17 Cr 18 ti 18 Mn20 Fe 2 1
Cobalt or nickel 22 copper 23 zinc 25 yttrium 24 zinc 26 arsenic 27 selenium 28
Br29 Rb30 Sr3 1 Ce or La33 Zr32 V or Mo34 Ro or Ru35.
pd36 Ag37 Cd38 V40 Sn39 sb 4 1 Fe43
I42 Cs44 Ba or V45 Ta46 W47 Nb48 Au49
Pt or IR 50 TL 53 Pb 54 th 56 Hg 52 bi 55 OS 51
Second, the discovery of the periodic law of elements.
1869 In March, Russian chemist Mendeleev (1834- 1907) published a paper, which listed the periodic table of elements and put forward the periodic law of elements-the properties of elements change periodically with the increase of atomic weight of elements. He pointed out in his paper: "Elements arranged according to atomic weight are obviously periodic in nature." "The atomic weight determines the characteristics of elements." "Some similar elements without elements will be found according to their atomic weights."
1869 65438+February, the German chemist Meyer (J.L. 1830- 1895) published his periodic table independently, clearly pointing out that the properties of elements are functions of their atomic weights. In his table, there is a family of transitional elements.
Why can Mendeleev's theory overcome the previous and contemporary theories and monopolize the right to discover the periodic law of elements? Analyzing this important case in the history of science, we can see that Mendeleev's theory is superior to other theories in the following aspects:
Rich in materials.
During the pre-Mendeleev period, few elements and related materials were found, and the classification work was limited to some elements, rather than considering all elements as a whole, so it could not explain the past and existing experimental facts and chemical phenomena well.
During Mendeleev's period, the elements found accounted for half of all elements (elements in the current periodic table), and the related knowledge of these elements, such as physical properties, chemical properties, valence, etc. A major breakthrough has been made in the method of determining the properties of elements, especially in the determination of atomic weight. 1860, at the world congress of chemists, chemists unanimously agreed to form a unified atomic weight determination method and atomic scale of the system. Mendeleev attended the meeting and accepted avogadro's molecular theory. This prompted him to put forward the correct periodic law of elements.
2. Good self-consistency.
Newlands arranged the elements mechanically according to the atomic weight measured at that time, without estimating the error of the atomic weight value or considering the undiscovered elements, so it is difficult to clearly reveal the internal laws of things. The confusion within the theory attracted ridicule and ridicule from others. Meyer made the same mistake. Mendeleev boldly modified some atomic weights, thus eliminating the contradictions within the theory. If it was recognized at that time that the atomic weight of gold was 169.2, then gold should be ranked before osmium 198.6 and iridium 196.7, and Mendeleev thought it should be ranked after these elements. After re-determination, the atomic weights of these elements are osmium 190.9, iridium 193. 1, platinum 195.2 and gold 197.2 respectively. Facts have proved Mendeleev's correctness. In addition, he boldly modified the atomic weights of uranium, indium, lanthanum, yttrium, erbium, cerium and thorium.
3. Good foresight.
Mendeleev left four spaces in the table for undiscovered elements, and listed six spaces in the new table of 187 1, and predicted the existence and properties of these elements. Although Meyer also left spaces in the table, he did not predict the nature of unknown elements.
1875, French chemist Abd Lang (P.E.L.1838-1912) discovered a new element called gallium (known as Galia in ancient France) when analyzing sphalerite in the Pyrenees. This is just the discovery of a new element ── the 65th element, which is nothing wonderful and surprising in itself. However, to the surprise of the discoverer of gallium, a letter with strange handwriting was sent from St. Petersburg. The letter said that the properties of gallium he found were not completely correct, especially the specific gravity of metal should be between 5.9 and 6.0, instead of 4.7 calculated by Aboud Lang. Signed "Professor Di Mudri Mendeleev of St. Petersburg University". Bu Abu Lang is the only person in the world who has just discovered gallium. How can a Russian professor who has never seen gallium say such a thing?
Bou-Abboud Lang was deeply touched. But he is a real scientist after all, and he treats this matter with a rigorous scientific attitude. He re-measured the specific gravity of pure gallium, which was 5.96. Anger turned into admiration. Abd Lang wrote in a paper: "I don't think it is necessary to explain the significance of Mr. Mendeleev's theory." This is the first time in the history of science to predict the discovery of a new element in advance.
1879, Swedish chemist Nelson L.F. 1840- 1899 discovered the second element "boron-like" predicted and described in detail by Mendeleev. Nelson called it scandium. He wrote: The ideas of Russian chemists have been most clearly proved.
1885, German chemist Winkler discovered the element germanium. In 1870, Mendeleev predicted the properties of this element, which he called "silicon-like". As soon as Winkler's paper came out, people compared it with Mendeleev's prediction 15 years ago, which is an amazing coincidence. The inventor himself said: there may be no more obvious example to prove the correctness of the theory of periodic law of elements.
1895, British chemist Ramsey (W.1852-1916) and others discovered a series of inert gas elements such as helium, argon and xenon. 1899, Madame Curie and others discovered radioactive elements such as polonium and radium, which all sat in the predetermined positions in Mendeleev's periodic table. In addition, the vacancy left in the Mn column was later dug up by the boss of the power company at a high price. 1925, German chemist Nord Dyke. W. 1893- 1960 and his wife discovered it-rhenium, an excellent filament element for making incandescent lamps. These are great victories of scientific thinking.
So the discovery of this theory is described as follows: on the road of science, there is a gem, which is the periodic law of elements. Lavoisier, D 'Urberville, Newlands, Meyer and others walked past it, picked it up, looked at it and threw it away. It was Mendeleev who absorbed the previous experience and studied it carefully to make it shine. Finally, he took this gem to the peak of chemistry and unified the whole inorganic chemistry. The above is a summary of the periodic table and periodic law. Please correct the shortcomings! 2065438+February 25, 2003 15: 58