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The periodic law, or the periodic system, is a classification of the chemical elements formulated by Russian chemist Dmitri Mendeleev. Mendeleev's work built on the efforts of several other scientists, including French geologist Alexandre-Émile Béguyer de Chancourtois, who was the first to use a periodic arrangement of all known elements. Mendeleev's law, first announced in 1869, stated that elements arranged according to the value of their atomic weights present a clear periodicity of properties. This allowed him to create a systematic table of all the 70 elements known at the time, which became the foundation of modern chemistry.
| Characteristics | Values |
|---|---|
| Name | Dmitri Mendeleev |
| Birth Date | 8 February 1834 |
| Birth Place | Verkhnie Aremzyani, near Tobolsk in Siberia, Russian Empire |
| Father's Name | Ivan Mendeleev/Ivan Pavlovich Mendeleev/Ivan |
| Mother's Name | Mariya Kornileva/Mariya Dmitrievna Mendeleeva/Mariya Kornilieva/Mariya Dmitrievna Mendeleeva |
| Occupation | Russian chemist |
| Known For | Formulating the periodic law and creating a version of the periodic table of elements |
| Year of Discovery | 1869 |
| Predicted Elements | Gallium, Scandium, Germanium |
| Other Contributions | Investigated the composition of petroleum and helped found the first oil refinery in Russia |
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What You'll Learn
John Newlands' Law of Octaves
John Newlands, a British chemist, was the first to arrange the elements into a periodic table with increasing order of atomic masses. He found that every eight elements had similar properties and called this the Law of Octaves. In 1864, Newlands attempted to combine the 62 elements known at the time. He arranged them in ascending order according to their atomic weights and discovered that the properties of every eighth element were the same. For instance, lithium, sodium, and potassium have similar chemical properties. Chlorine is the eighth element after fluorine, and they share similar chemical properties.
Newlands' Law of Octaves was one of the initial attempts to arrange all the known chemical elements in a table to make their study better. This law establishes a framework for classifying items with comparable features into groups. It was not until years later that another more extensive periodic table effort would gain much greater acceptance, and that the pioneering work of John Newlands would be appreciated.
Newlands' periodic classification had some limitations. Some elements that were not similar were grouped together. For example, nickel and cobalt were placed in the same slot. Also, the octave layout was unable to accommodate later discovered components. As a result, new elements could not be discovered using this classification scheme. The Law of Octaves hold true only up to calcium. Elements with higher atomic masses had atomic masses that were too large to fit within octaves.
Despite Newlands' contributions, it was Russian chemist Dmitri Mendeleev who gained recognition for formulating the periodic law and creating a version of the periodic table of elements. Mendeleev's table was the first bold attempt to arrange all the known elements in a proper manner. He used the periodic law not only to correct the then-accepted properties of some known elements but also to predict the properties of three elements that were yet to be discovered. Mendeleev's table left gaps for undiscovered elements, and he predicted the properties of some of these elements. The later discovery of these elements, including gallium, scandium, and germanium, verified his predictions and his periodic table won universal recognition.
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Mendeleev's 1869 presentation
The Russian chemist, Dmitri Mendeleev, made a formal presentation to the Russian Chemical Society on 6 March 1869. The presentation was titled 'The Dependence between the Properties of the Atomic Weights of the Elements', and it described elements according to both atomic weight (now called relative atomic mass) and valence. Mendeleev's presentation stated that the elements, if arranged according to their atomic weight, exhibit an apparent periodicity of properties. This meant that elements with similar chemical properties either had similar atomic weights (e.g. Pt, Ir, Os) or had atomic weights that increased regularly (e.g. K, Rb, Cs).
Mendeleev's work built on that of previous scientists. For example, in 1789, French chemist Antoine Lavoisier tried grouping the elements as metals and nonmetals. In 1829, German physicist Johann Wolfang Döbereiner observed similarities in the physical and chemical properties of certain elements, arranging them in groups of three in increasing order of atomic weight and calling them triads. British chemist John Newlands also made a similar discovery in 1864, noting that elements with atomic weights that differed by seven exhibited similar properties. He called this the Law of Octaves. Mendeleev, however, was the first to publish a version of the table that we would recognise today.
Mendeleev's periodic table was not without its flaws. For example, he was puzzled about where to put the known lanthanides, and he incorrectly predicted that iodine had a lower atomic weight than tellurium. However, his later discovery of elements predicted by his table, including gallium (1875), scandium (1879), and germanium (1886), verified his predictions and his periodic table won universal recognition. In 1955, the 101st element was named mendelevium in his honour.
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Lothar Meyer's periodic table
The modern periodic table arranges the elements by their atomic numbers and chemical properties. Several scientists worked for almost a century to assemble the elements into this format.
Lothar Meyer, a German chemist, was one of the pioneers in developing the earliest versions of the periodic table of chemical elements. Meyer produced several periodic tables between 1864 and 1870. In 1859, Meyer began his career as a science educator. He held various appointments before serving as a professor of chemistry at the University of Tübingen from 1876 to 1895. Meyer's book, 'Die modernen Theorien der Chemie' (1864), contained a preliminary scheme for arranging elements by atomic weight and discussed the relation between atomic weights and the properties of the elements. This influential work was often enlarged and went into many editions. Meyer's 1864 book contained an early version of the periodic table, with 28 elements grouped for the first time into six families by their valence. Meyer also included a table in his book that ordered elements by increasing atomic weight.
Meyer's work on the periodic table was influenced by a paper given by Stanislao Cannizzaro in 1860, which called attention to Avogadro's hypothesis about atoms and molecules. Meyer was also influenced by the mathematical teaching of Gustav Kirchhoff. Meyer's work on the periodic table was independent of Dmitry Mendeleev's work, though the two scientists would have known each other from their shared time at Heidelberg University. Meyer's 1870 table was a graph relating atomic volume and atomic number and clearly showing the periodic relationships of the elements. Meyer did not emphasize his predictions of future elements or suggest details of their physical and chemical properties.
In 1882, the Royal Society of London awarded the Davy Medal jointly to Mendeleev and Meyer for their work on the Periodic Law. In 1983, the mineral lotharmeyerite was discovered and named in recognition of Meyer's work on the Periodic Law.
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Mendeleev's law of periodicity
The Russian chemist, Dmitri Mendeleev, is known for formulating the periodic law and creating a version of the periodic table of elements. Mendeleev's law of periodicity states that "the properties of elements are the periodic function of their atomic masses". This law was based on Mendeleev's observation that elements with similar characteristics could be arranged in vertical columns, known as groups, in his periodic table. Mendeleev's table had seven rows, known as periods, with increasing atomic numbers from left to right and 18 vertical columns.
Mendeleev's work built upon the efforts of previous scientists who had also attempted to classify and group elements based on their properties. For example, in 1789, French chemist Antoine Lavoisier grouped the elements as metals and non-metals, while German physicist Johann Wolfgang Döbereiner identified triads of elements with similar properties in 1817. British chemist John Newlands also contributed to the development of the periodic table by arranging the elements in eight groups based on their atomic masses, which he called the Law of Octaves.
However, Mendeleev's periodic table was a significant improvement over these earlier attempts. It was the first periodic table that we would recognize today and provided a framework for the modern periodic table. Mendeleev's table included gaps for undiscovered elements and exhibited mostly accurate values for atomic mass. Mendeleev's law of periodicity and his contributions to the development of the periodic table were recognized during his lifetime, and he received numerous nominations for the Nobel Prize in Chemistry. In 1906, the Nobel Committee for Chemistry recommended awarding the Nobel Prize in Chemistry to Mendeleev for his discovery of the periodic system.
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Mendeleev's legacy
While several scientists contributed to the development of the periodic table, Russian chemist Dmitri Mendeleev is widely recognised for formulating the periodic law and creating the first version of the periodic table that we would recognise today. Mendeleev's legacy lies in his recognition of the periodic system, which has had a profound impact on the field of chemistry and beyond.
Mendeleev's Periodic System
Mendeleev's periodic system, introduced in 1869, was a groundbreaking achievement. It provided a framework for organising all the known chemical elements based on their atomic weights and chemical similarities. This system was a significant advancement from previous attempts to classify elements, which lacked a standardised structure. Mendeleev's table arranged the elements in horizontal rows, known as periods, with metals on the left and non-metals on the right. The vertical columns, or groups, consisted of elements with similar chemical properties. This arrangement allowed for a better understanding of the relationships between elements and their properties.
Prediction of Undiscovered Elements
One of Mendeleev's most notable contributions was his prediction of undiscovered elements. In his periodic table, Mendeleev left gaps for elements that had not yet been discovered, challenging the notion that the list of elements was complete at the time. He even predicted the properties of these unknown elements, giving them names like "eka-aluminium" (later discovered as gallium). The subsequent discovery of these elements, including gallium, scandium, and germanium, validated Mendeleev's predictions and solidified the accuracy of his periodic system.
Impact on Education and Science
Mendeleev's periodic table revolutionised the way chemistry was taught and studied. Students were no longer required to memorise the properties of individual elements. Instead, they could learn the properties of elements within each column and make predictions about other group members. This made the subject more accessible and interesting, even for those outside the field. Mendeleev's table also had far-reaching implications for various scientific disciplines, including physics, biology, engineering, medicine, and geology. It provided a tool to understand the atomic structure of elements and their chemical similarities and differences, enabling scientists to design experiments and develop new chemicals for use in industries such as pharmaceuticals, cosmetics, and technology.
Honours and Recognition
Mendeleev's contributions were recognised during his lifetime and continue to be celebrated even a century after his death. He received numerous honours, including the Davy Medal from the Royal Society of London in 1882, shared with Lothar Meyer. Mendeleev was also nominated for the Nobel Prize in Chemistry several times during the last three years of his life. In 1905, he was elected a member of the Royal Swedish Academy of Sciences. Additionally, UNESCO named 2019 the International Year of the Periodic Table, marking the 150th anniversary of Mendeleev's publication. The element 101, discovered in 1955, was named mendelevium in his honour, further commemorating his legacy in the field of chemistry.
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Frequently asked questions
Russian chemist Dmitri Mendeleev is credited with formulating the periodic law for the first time in his 1871 article "Periodic regularity of the chemical elements".
While Mendeleev created a version of the periodic table, he was not the first to attempt to group the elements. French geologist Alexandre-Émile Béguyer de Chancourtois noticed that elements displayed similar properties at regular intervals when ordered by their atomic weights. He devised a three-dimensional chart named the "telluric helix" in 1862.
Mendeleev likely knew German chemist Lothar Meyer, who trained at Heidelberg University under Bunsen and Kirchhoff, as Mendeleev did. Meyer produced several periodic tables between 1864 and 1870.
Mendeleev faced challenges due to the inaccurate determination of atomic weights at the time. He questioned some of the accepted atomic weights, pointing out that they did not correspond to those suggested by his Periodic Law. Despite these challenges, Mendeleev's periodic table gained universal recognition by 1890.
