Question

Difference between dobereiner periodic table and modern periodic table

Answer 1

When scientists began to classify and organize the elements, about 63 elements were known. Many, like gold, silver, tin, copper, lead, and mercury had been known since antiquity. Phosphorus was discovered in 1669. Many more elements were discovered over the next 220 years. During this time, scientists determined the masses of the individual elements. They learned many other chemical properties by methodically exposing individual elements to various chemicals and observing the reactions. As more information was learned about individual elements, scientists wanted to organize the elements in a useful way. From 1817 through the time of Mendeleev, many scientists made important contributions to what would become the modern periodic table.

In 1817, Johann Dobereiner noticed that the atomic mass of strontium was halfway between those of calcium and barium. These three elements had similar properties. Dobereiner discovered more of these sets of three and called it the Law of Triads.In 1862, A. E. Beguyer de Chancourtois arranged the elements on a cylinder, with the elements wrapping around the cylinder. On this three-dimensional table, the elements lined up in vertical columns.In 1863, John Newlands published a table with elements arranged in groups of eight proposing the elements followed the Law of Octaves.

Newlands’ table was not well received because two elements were in the same box in several spots on his table. In the late 1800s, Lothar Meyer was developing a periodic table at the same time as Mendeleev. Meyer’s periodic table was very similar to Mendeleev’s, but because it was published after Mendeleev’s, Mendeleev got most of the credit. Mendeleev has been called the “father of the periodic table”.

Mendeleev’s Table

Dmitri Mendeleev was born in 1834 in Russia. He was the youngest of 13 (or 11, 14, or 17, depending on the source) children. Mendeleev was interested in many fields of science and studied a wide variety of science topics throughout his life. As a child he learned about chemistry in his mother’s glassblowing factory. At university, he earned an advanced degree in chemistry while training as a teacher. While teaching chemistry as a professor at the University of St. Petersburg, Mendeleev felt that there were no adequate textbooks for teaching chemistry, so he began to write his own. While working on his textbook from 1868–1870, he began formulating ideas for a way to organize the elements. Mendeleev’s fist attempt to organize the elements is seen in In his first periodic table Mendeleev arranged the elements by their mass and other chemical properties. At the time, the underlying chemical structure of atoms was not known.
Mendeleev expanded his periodic table to include all the elements known at the time. This version of the periodic table was published in 1869. A draft of this periodic table, in Mendeleev’s own writing,

Mendeleev continued to refine his periodic table, publishing a new version in 1871. In this version, because of the patterns Mendeleev observed, he was able to notice holes in the patterns and predict that there were elements that had not yet been discovered that would fill those holes. Although some scientists were skeptical of this table, when new elements were discovered and some of Mendeleev’s predictions were supported by evidence, his periodic table became accepted by the scientific community. Further refinements to the periodic table have been made, including the addition of new elements, to create the modern periodic table

Answer 2

dobereiner's, in 1829,grouped certain element in the group of three,called traids. the three element in a triad had similar chemical properety