The periodic table
The arrangement of the elements by atomic weight into rows and columns, so that chemically similar elements line up — a pattern so strong it let Mendeleev leave gaps for elements not yet discovered and predict their properties in advance.
الأرشيف العميق مكتوب بالإنجليزية حتى الآن — والترجمات المتحقَّق منها جزء من خارطة الطريق. خاصية الترجمة في متصفحك تعمل جيدًا في هذه الصفحة.
✦ مهلًا، حقًّا؟
In 1875 a Frenchman, Lecoq de Boisbaudran, discovered gallium and measured its density at 4.7. Mendeleev, who had predicted this element and never held a grain of it, wrote from Russia to say the measurement was wrong — his table required a density near 5.9. Lecoq remeasured a purer sample and got 5.9. The table had corrected the man who found the element.
ما هو
The periodic table is the map that shows the elements are not a random list but a repeating pattern. Lay them out in order of atomic weight and their properties rise and fall on a cycle: after a very reactive light metal comes a run of elements that grade toward a violently reactive nonmetal and then an inert gas, and then the cycle starts again. Put each new cycle on a new row and the recurring types stack into vertical families. The table is that periodicity, drawn.
لماذا كان مهمًّا
Several people noticed the recurrence, but Mendeleev trusted the pattern more than the data. Where an element's weight would have placed it in the wrong chemical family, he assumed the weight was mismeasured or that an undiscovered element belonged in between — and left holes. Then he did what no mere classification does: he predicted the missing elements' weights, densities, and chemistry from their empty seats. When gallium (1875), scandium (1879), and germanium (1886) turned up matching his forecasts, the table stopped being a bookkeeping convenience and became a law of nature that could be interrogated.
ما الذي أتاحه
A framework that made chemistry teachable and predictable, and a research program: every gap was a wanted poster for an element, and the noble gases, several metals, and the whole layout of the rare earths were slotted in by following it. It also posed the question that atomic physics would answer — why the period lengths are 2, 8, 8, 18 — and so pointed straight at the structure of the atom that underlies all of it.
أدنى نسخة صالحة للعمل
List the known elements in order of increasing atomic weight and start a new row each time chemical behavior repeats, so that families — the soft reactive metals, the choking halogens — fall into the same column. Where the weight order would break a family, leave a gap rather than force the fit.
هذا المدخل في انتظار سرده الكامل — رسّامو الخرائط يعملون عليه. أما موضعه في الشبكة فمُتحقَّق منه بالفعل.
خيوط تمرّ بهذه القدرة
How did ore become stainless steel?7 خطوةالمصادر
- — Dmitri Mendeleev, 'The relation between the properties and atomic weights of the elements' (1869)
- — Eric Scerri, *The Periodic Table: Its Story and Its Significance* (2007)
هل في هذه الصفحة خطأ؟ كل زعم هنا كُتب ليصمد أمام التحدي. اقترح تصحيحًا →