Why Is the Gear of the Elemental Triads Locked UPDATED
Why Is the Gear of the Elemental Triads Locked
In the history of the periodic table, Döbereiner's triads were an early endeavour to sort the elements into some logical gild and sets based on their physical properties. They are analogous to the groups (columns) on the modern periodic table.
In 1817, a letter past Ferdinand Wurzer reported Johann Wolfgang Döbereiner's observations of the alkaline earths; namely, that strontium had properties that were intermediate to those of calcium and barium.[1] By 1829, Döbereiner had found other groups of 3 elements (hence "triads") whose physical properties were similarly related.[2] He also noted that some quantifiable properties of elements (e.k. diminutive weight and density) in a triad followed a trend whereby the value of the eye element in the triad would be exactly or nearly predicted by taking the arithmetic mean of values for that property of the other two elements. These are as follows:
| Triad name[2] | Elements and atomic masses[2] [iii] | ||
|---|---|---|---|
| Element 1 mass | Element 2 Mean of ane and 3 Actual mass | Element 3 mass | |
| Alkali-forming elements | Lithium half-dozen.941 u | Sodium 22.989769 u 23.01965 u | Potassium 39.0983 u |
| Alkaline-earth-forming elements [ atomic masses verification needed ] | Calcium 40.078 u | Strontium 87.62 u 88.7025 u | Barium 137.327 u |
| Salt-forming elements | Chlorine 35.470 u | Bromine 79.904 u 81.187 u | Iodine 126.904 u |
| Acid-forming elements | Sulfur 32.065 u | Selenium 78.971 u 79.8325 u | Tellurium 127.lx u |
Limitations:
All the known elements could non exist bundled in the grade of triads. For very depression-mass or very high mass elements, the Döbereiner'south triads are not applicable. Accept the example of F (Fluorine), Cl (Chlorine), and Br (Bromine). The atomic mass of Cl is not an arithmetic mean of the atomic masses of F and Br. Every bit the techniques for accurately measuring diminutive masses improved, the Döbereiner's triad was found to fail to remain strictly valid.
References [edit]
- ^ Wurzer, Ferdinand (1817). "Auszug eines Briefes vom Hofrath Wurzer, Prof. der Chemie zu Marburg" [Excerpt of a alphabetic character from Court Advisor Wurzer, Professor of Chemistry at Marburg]. Annalen der Physik (in German). 56 (7): 331–334. Bibcode:1817AnP....56..331.. doi:x.1002/andp.18170560709. From pp. 332–333: "In der Gegend von Jena (bei Dornburg) … Schwerspaths seyn möchte." (In the expanse of Jena (nearly Dornburg) it is known that celestine has been discovered in large quantities. This gave Mr. Döbereiner cause to inquire rigorously into the stoichiometric value of strontium oxide by a great series of experiments. It turned out that it [i.e., the molar weight of strontium oxide] – if that of hydrogen is expressed by ane or that of oxygen is expressed by the number 7.5 – is equal to 50. This number is, however, precisely the arithmetic hateful of that which denotes the stoichiometric value of calcium oxide (= 27.55) and of that which denotes the stoichiometric value of barium oxide (= 72.5) ; namely (27.5 + 72.5) / two = fifty. For a moment, Mr. Döbereiner institute himself thereby acquired to dubiety the independent being of strontium; withal, this withstood both his analytical and synthetic experiments. Fifty-fifty more noteworthy is the circumstance that the specific weight of strontium sulfide is besides the arithmetic mean of that of pure (water-free) calcium sulfide and that [i.east., the sulfide] of barium, namely (two.9 + iv.40) / 2 = 3.65 ; which must cause [i] to believe fifty-fifty more that celestine might be a mixture of equal stoichiometric amounts of anhydrite [i.e., anhydrous calcium sulfate] and barite.)
- ^ a b c Döbereiner, J. W. (1829). "Versuch zu einer Gruppirung der elementaren Stoffe nach ihrer Analogie" [An attempt to group simple substances co-ordinate to their analogies]. Annalen der Physik und Chemie. 2d series (in German). 15 (2): 301–307. Bibcode:1829AnP....91..301D. doi:10.1002/andp.18290910217. For an English translation of this article, see: Johann Wolfgang Döbereiner: "An Attempt to Group Unproblematic Substances co-ordinate to Their Analogies" (Lemoyne College (Syracuse, New York, The states))
- ^ "Johann Wolfgang Dobereiner". Archived from the original on 2016-03-23. Retrieved 2016-03-23 .
- "A Historic Overview: Mendeleev and the Periodic Table" (PDF) . Retrieved 2013-01-15 .
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Why Is the Gear of the Elemental Triads Locked UPDATED
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