what is the symbol of universal quantifier
Answers
Explanation:
They were R2O, R2O2, R2O3, R2O4, R2O5, R2O6, and R2O7. The list was later appended with R2O8.
Scerri notes that this table "does not include elements such as astatine and actinium, which he [Mendeleev] predicted successfully but did not name. Neither does it include predictions that were represented just by dashes in Mendeleev’s periodic systems. Among some other failures, not included in the table, is an inert gas element between barium and tantalum, which would have been called ekaxenon, although Mendeleev did not refer to it as such."[33]
He noted similarity despite sequential atomic weights; he termed such sequences as primary groups (as opposed to regular secondary groups, those in the likes of the halogens or the alkali metals). Other examples of primary groups included set of rhodium, ruthenium, and palladium, and the set of iridium, osmium, and platinum.
Mendeleev referred to Brauner in this manner after Brauner measured the atomic weight of tellurium and obtained the value 125. Mendeleev had thought that due to the properties tellurium and iodine display, the latter should be the heavier one while the contemporary data pointed otherwise (tellurium was assessed with the value of 128, and iodine 127). Later measurements by Brauner himself, however, showed the correctness of the original measurement; Mendeleev doubted it for the rest of his life.[41]
Notably, Mendeleev did not immediately identify germanium as eka-silicium. Winkler explained, "The present case, however, shows quite clearly how deceptive it can be to use analogies, because the tetradic value of germanium has meanwhile become an irrefutable fact, and there can be no doubt that the new element is nothing other than "eka-silicium" predicted by Mendeleev fifteen years ago. This identification comes from the short and still very imperfect characteristic of germanium that I gave at the beginning and was first decisively pronounced by V. v. Richter. Almost at the same time, Mendeleev, the deserving creator of the periodic system, commented that although several of the properties of germanium I mentioned reminded of those of eka-silicium, the observed liquidity of the element indicated the possibility of placing it elsewhere in the periodic system. Lothar Meyer declared the germanium to be eka-silicium from the beginning, adding that according to the atomic volume curve produced by it, contrary to Mendeleev's assumption, it had to be easily meltable and probably also easy to vaporize. At that time the germanium had not yet been presented in the reguline state; it is all the more remarkable that, as will be shown below, Lothar Meyer's condition has, to some extent, really come true."[50]
Meyer's tables, in contrast, did not at all attempt to incorporate those elements.[citation needed]
The only other monatomic gas known at the time was vaporized mercury.[57]
Mendeleev did consider that some atomic weight values could be missing from the set of known values. However, Mendeleev could not have made a prediction of a group of unreactive gases in a fashion similar to the one in which he made his predictions on reactive elements and their chemical properties.[66]
The notion of ether was disproven by German physicist Albert Einstein in 1905 with his special theory of relativity; the idea that ether did not exist was accepted in the scientific community rather quickly.
Explanation: They were R2O, R2O2, R2O3, R2O4, R2O5, R2O6, and R2O7.