27 quotes found
"1. The elements, if arranged according to their atomic weights, exhibit an evident periodicity of properties. 2. Elements which are similar as regards their chemical properties have atomic weights which are either of nearly the same value (e.g., platinum, iridium, osmium) or which increase regularly (e.g., potassium, rubidium, caesium). 3. The arrangement of the elements, or of groups of elements in the order of their atomic weights corresponds to their so-called valencies as well as, to some extent, to their distinctive chemical properties--as is apparent among other series in that of lithium, beryllium, barium, carbon, nitrogen, oxygen and iron [sic. The printed speech in J. Chem. Soc. says barium and iron. Obviously boron (B) and fluorine (F) are meant. Mendeleev's 1869 paper lists the symbols B and F rather than the names of the elements.--CJG] 4. The elements which are the most widely diffused have small atomic weights. 5. The magnitude of the atomic weight determines the character of the element just as the magnitude of the molecule determines the character of a compound body. 6. We must expect the discovery of many yet unknown elements, for example, elements analogous to aluminium and silicon, whose atomic weight would be between 65 and 75. 7. The atomic weight of an element may sometimes be amended by a knowledge of those of the contiguous elements. Thus, the atomic weight of tellurium must lie between 123 and 126, and cannot be 128. 8. Certain characteristic properties of the elements can be foretold from their atomic weights. ...[R]elations ...exist between the atomic weights of dissimilar elements ...hitherto ...neglected. I believe that the solution of some of the most important problems of our science lies in researches of this kind. To-day, 20 years after the above conclusions were formulated, they may still be considered as expressing the essence of the now well-known periodic law."
"In science we must all submit not to what seems to us attractive from one point of view or another, but to what represents an agreement between theory and experiment."
"To burn oil!.. You can fuel with money as well."
"Doctor, you have science, I have faith.--to his physician, this was possibly a Jules Verne quote."
"I wish to establish some sort of system not guided by chance but by some sort of definite and exact principle."
"We should still expect to discover many unknown simple bodies; for example, those similar to aluminum and silicon, elements with atomic weights of 65 to 75."
"I have no need of proof. The laws of nature, unlike the laws of grammar, admit of no exception."
"I suppose when my unknown elements are found, more people will pay us attention."
"The occultist has the satisfaction of knowing that the great Russian chemist, Mendeleef, preferred the atomic theory. In Sir William Tilden's recent book entitled "Chemical Discovery and Invention in the Twentieth Century," I read that Mendeleef, "disregarding conventional views," supposed the ether to have a molecular or atomic structure, and in time all physicists must come to recognise that the Electron is not, as so many suppose at present, an atom of electricity, but an atom of ether carrying a definite unit charge of electricity."
"Even though Mendeleev always denied that electrons exist, they later turned out to be vital for ordering the elements in his table."
"His stroke of genius was to leave gaps for elements that were still to be discovered, predicting what their properties should be from his table. This was a tremendous publicity coup! A few years later, new elements were discovered with properties which matched almost exactly with Mendeleev's predictions - the case was won..."
"When Mendeleev began teaching at the University, there were 63 known elements, each identified by atomic weights newly determined by Avogadro's hypothesis. He had to develop some system of classification. The two basic methods for dividing the elements—into metals and metalloids (nonmetals) or by using the new concept of valency—seemed unhelpful to Mendeleev. He chose to write his own textbook instead and work out the challenges of classification himself."
"Mendeleev was not concerned in 1869 with establishing a basic law of chemistry. He was concerned with writing a textbook for young chemists at St. Petersburg University. ...From 1871 on, Mendeleev himself would repeatedly abstract periodicity from its context... making it seem an emblem of pure science. ...it is how those sketches turned into an immutable law that requires explaining....Mendeleev's predictions themselves had naturalized periodicity by demonstrating the predictive power of his system. He then used this success to naturalize other components of the Great Reforms model."
"The distinction would only come to Mendeleev halfway through writing his Principles of Chemistry. ...chemical practice and not chemical theory had provided his initial organizing principle... Up to this point [Chapter 20], Mendeleev had only treated four elements in any detail: oxygen, carbon, nitrogen, and hydrogen—the so-called "organogens." Mendeleev began this chapter as usual by purifying the central substance, sodium chloride, from sources such as seawater. A discussion of sodium and chlorine followed in the next few chapters, and finally the halogens appeared... that were closely related to chlorine... and the alkali metals (the sodium family) form the first chapter of volume 2. ...he had dealt with only 8 elements, relegating 55... to the second volume. ...Mendeleev's earlier system of pedalogically useful organization—using laboratory practices... could no longer sustain the burden of exposition. He needed a new system... and he hit upon the idea of using a numerical marker for each element. Atomic weight seemed the most likely candidate for a system that would (a) account for all remaining elements; (b) do so in limited space; and (c) maintain some pedagogical merit. His solution, the periodic system, remains one of the most useful tools in chemistry."
"He made up a pack of cards and wrote an element and its atomic weight on each... So began the most memorable card game in the history of science. He called it "chemical solitaire" and began laying out the cards... to see if there was a pattern... [P]reviously chemists had grouped the elements in one of two ways, either by their properties... or by... their atomic weight, which is what Berzelius and Cannizzaro had done. Mendeleev's great genius was to combine those two methods together. ...Little more than half the elements ...had been discovered, so he was playing with an incomplete deck of cards. He stayed up for three days and three nights without... sleep... finally dozed off... [and] had an extraordinary dream. He saw almost all of the 63 known elements... in a grand table which related them together."
"Sandro was surprised when I tried to explain to him some of the ideas that at the time I was confusedly cultivating. That the nobility of man, acquired in a hundred centuries of trial and error, lay in making himself the conquerer of matter, and that I had enrolled in chemistry because I wanted to remain faithful to this nobility. That conquering matter is to understand it, and understanding matter is necessary to understanding the universe and ourselves: and that therefore Mendeleev's Periodic Table, which just during those weeks we were laboriously learning to unravel, was poetry, loftier and more solemn than all the poetry we had swallowed down in liceo; and come to think of it, it even rhymed!"
"In writing a textbook of general chemistry, Mendeleev devoted separate chapters to families of elements with similar properties, including the alkali metals, the alkaline earth metals, and the halogens. Reflecting on the properties of these and other elements, he proposed in 1869 a primitive version of today's periodic table. Indeed, he predicted detailed properties for three such elements (scandium, gallium, and germanium). By 1886 all of these elements had been discovered and found to have properties very similar to those he had predicted."
"Mendeleev noticed that there were regular repeating patterns and similarities between different elements when they were ordered in terms of their atomic weights. Atomic weight was originally calculated from the average mass of one mole of the element relative to hydrogen (though the modern comparison is with carbon-12...). However, even Mendeleev was aware that classification based on atomic weight was flawed; for example, the elements tellurium and iodine occurred in the wrong order on the basis of their atomic weight, with iodine having a lower atomic weight but rightly having the properties of the halogen group (chlorine, fluorine, etc)... Mendeleev therefore decided to reverse the periodic sequence in their case. It was only in the twentieth century, when the structure of the atom based on the protons and the neutrons was identified, that the use of atomic number rather than atomic weight provided the ideal basis for the periodic table classification system. The atomic number of an element refers to its number of protons... Because the chemical properties of an element are determined by the number of negatively charged electrons, which in the non-ionozed form of the element matches the number of protons, there are many elements that have a number of isotopes, that is, have different numbers of neutrons, affecting the atomic weight but not the atomic number. Hence, Mendeleev's tellurium and iodine anomoly turned out to be because the tellurium he had sourced contained a preponderance of a heavier tellurium isotope giving it a greater atomic weight than idodine."
"Despite Mendeleev's initial system being flawed, and the correct theoretical basis of the periodic table not being identified for another 50 years, Mendeleev was able to predict correctly a number of elements that had yet to be identified but which were expected to exist if the repeating periodic structure of the table was correct. These elements included gallium and germanium, whose properties Mendeleev had been able to outline because of their membership in groups of poor metals that included known elements such as aluminum and silicon, respectively (hence Mendeleev's original names of "eka-aluminum" for gallium and "eka-silicon" for germanium). One of the great strengths of a theoretically based classification system, therefore, is that it can predict the existence of yet-to-be identified members of the system or can lead to a reclassification of members that have been misclassified under previous systems."
"Germanium, which name you should preserve since you are factually its father, is the element eka-silicon, Es-73, predicted by Mendeleev, the lowest homolog of tin, standing in the first large period between Ga (69.8) and As (79.9)... Eka-siicon is the element which we have awaited with great anticipation, and in any case the immediate study of germanium will be the most definitive experimentum crucis for the periodic system."
"Dimitri was writing a textbook and wanted to organize the elements properly. So he wrote each element onto its own card to help him sort them out. Dimitri enjoyed playing cards, especially patience, and one evening he dosed off while working. He had a dream in which each of the cards lined up in rows, just like a game of patience. When he woke, he realized that he should put the elements in order of atomic mass."
"Mendeleev... set about writing a book aimed at summarizing all of inorganic chemistry. It was while writing this book that he identified the organizing principle... the periodic system of the elements."
"Dimitri Mendeleev was probably the greatest scientist produced by Russia. ...the periodic table was developed by Mendeleev, as well as five other scientists, over a period of about 10 years, after the Italian chemist Cannizzaro had published a consistent set of atomic weights in 1860. It appears that Mendeleev was unaware of the work of several of his co-discoverers, however. ...What is not well known is that about half of the elements that Mendeleev predicted were never found."
"For Mendeleev the rare earths were a complete nightmare because he didn't know where to put them. He couldn't fit them in the table..! Five of them had been found by the time he was building the table, and so he... stuck them in somewhere where things went 3+, and then went "Uh?" and... left it at that. ...[T]his was a real problem, because no one knew where these building blocks went into the periodic table. ...[I]t wasn't ...until Moseley had established what was, that things began to fit together... and suddenly they realized that there couldn't be more than 14... [T]hen as the quantum mechanics rules came through it became clear... that... you'd found the hole. There was the gap... in , and so that became a target."
"The table of Mendeleeff was changed but little for thirty years. Its anomalies, as the omission of hydrogen and the rejection of the atomic weight as the deciding factor in such cases as cobalt and nickel, tellurium and iodine, etc., were recognized; but greater knowledge was needed before these could be explained or the underlying law grasped."
"The work of Mendeleev has lately thrown a new light upon the relations existing between the atomic weights of the elements and their properties. The latter are a function of the atomic weight, which function is periodic. It is not limited to such and such a group of elements, but embraces all of the elementary bodies of chemistry... thus dealing with the most varied and the most profound questions of science... in a word, regard the facts of chemistry from a lofty and comprehensive point of view."
"He formulated, as the fundamental law of the physico-chemical sciences, the dictum that "all the properties of bodies are periodic functions of their atomic weights"... on reaching this point of its development, the conception of Prof. Mendeleev becomes essentially injurious. Under the pretext of a law which has still to be demonstrated, it forbids us to throw light upon pure matters of observation, and forces us to remain in a vicious circle from which there is no escape. I think that it is time to show clearly that there is nothing [here] which merits the name of law or system."