5/27/2023 0 Comments S periodic table![]() Like alkali metals, hydrogen combines with halogens, oxygen, and sulfur to form compounds having similar formulae, as shown in the examples here. The electronic configuration of hydrogen resembles that of alkali metals. One of the strengths of Mendeléev’s Periodic Table was that, when these gases were discovered, they could be placed in a new group without disturbing the existing order. These gases were discovered very late because they are very inert and present in extremely low concentrations in our atmosphere. Noble gases like helium (He), neon (Ne), and argon (Ar) have been mentioned in many a context before this. This provided convincing evidence for both the correctness and usefulness of Mendeléev’s Periodic Table.įurther, it was the extraordinary success of Mendeléev’s prediction that led chemists not only to accept his Periodic Table but also recognize him, as the originator of the concept on which it is based. The properties of Eka–Aluminium predicted by Mendeléev and those of the element, gallium which was discovered later and replaced Ekaaluminium, are listed as follows Mendeléev named them by prefixing a Sanskrit numeral, Eka(one) to the name of the preceding element in the same group.įor instance, scandium, gallium and germanium, discovered later, have properties similar to Eka–boron, Eka–aluminum and Eka–silicon, respectively. Instead of looking upon these gaps as defects, Mendeléev boldly predicted the existence of some elements that had not been discovered at that time. For example, cobalt (atomic mass 58.9) appeared before nickel (atomic mass 58.7).įurther, Mendeléev left some gaps in his Periodic Table. The sequence was inverted so that elements with similar properties could be grouped together. While developing the Periodic Table, there were a few instances where Mendeléev had to place an element with a slightly greater atomic mass before an element with a slightly lower atomic mass. Mendeléev’s Periodic Table contains vertical columns called ‘groups’ and horizontal rows called ‘periods.Īchievements of Mendeléev’s Periodic Table On this basis, Mendeléev formulated a Periodic Law, which states that ‘the properties of elements are the periodic function of their atomic masses. It was also observed that there occurs a periodic recurrence of elements with similar physical and chemical properties. He observed that most of the elements got a place in a Periodic Table and were arranged in the order of their increasing atomic masses. He sorted out the elements with similar properties and pinned the cards together on a wall. He then took 63 cards and on each card he wrote down the properties of one element. The formulae of the hydrides and oxides formed by an element were treated as one of the basic properties of an element for its classification. He selected hydrogen and oxygen as they are very reactive and formed compounds with most elements. Among chemical properties, Mendeléev concentrated on the compounds formed by elements with oxygen and hydrogen. He examined the relationship between the atomic masses of the elements and their physical and chemical properties. When Mendeléev started his work, 63 elements were known. He was the most important contributor to the early development of a Periodic Table of elements wherein the elements were arranged on the basis of their fundamental property, the atomic mass, and also on the similarity of chemical properties. The main credit for classifying elements goes to Dmitri Ivanovich Mendeléev, a Russian chemist. Even after the rejection of Newlands’ Law of Octaves, many scientists continued to search for a pattern that correlated the properties of elements with their atomic masses. ![]()
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