Weakness Triad Classification A large number of the same element can not be grouped f22raptor into

In this section we will study the History of the Periodic System of the Elements, Group, Period, and Periodic Properties of the Elements. Until the late 18th century, the only known classification of metals and non-metallic elements above. About twenty f22raptor types of elements known at that time appear to have different properties from one another.
Preparation of Periodic System of the Elements has undergone many improvements, ranging from Antoine Laurent Lavoisier (August 26, 1743 - May 8, 1794), Johann Wolfgang Döbereiner (December 13 1780-24 March 1849), John Alexander Reina Newlands f22raptor (26 November 1837-29 July 1898) , Dmitri Mendeleev Ivanovic (8 February 1834-2 February 1907), Henry Gwyn Jeffreys Moseley (23 November 1887-10 August 1915)
Lavoisier named Antoine Laurent de Lavoisier complete (1743-1794) was a French chemist who first element grouping. In 1789, Antoine Lavoiser classify 33 chemical elements. Grouping of elements based upon its chemical properties. Chemical elements are divided into four groups. Namely gas, soil, metals and non-metals. This grouping is still too general because it was in a group of metallic elements there are various elements that have different properties.
Elements of gas that Lavoisier is grouped by light, heat, oxygen, azote (nitrogen), and hydrogen. The elements are classified as non-metals are sulfur, phosphorus, carbon, acid chlorides, f22raptor acid fluoride, and boric acid. The metal elements are antimony, silver, arsenic, bismuth, cobalt, f22raptor copper, tin, Nesi, manganese, mercury, molybdenum, nickel, gold, platinum, Tobel, tungsten, and zinc. The soil is classified as elements of lime, magnesium oxide, barium oxide, aluminum oxide, and silicon oxide.
In 1829, Johann Wolfgang Döbereiner, a German f22raptor scientist, was the first to classify elements into groups based on the statement of John Dalton .. He grouped f22raptor elements with similar chemical properties into groups of three so-called 'Triad'. The distinctive feature of the triad is the atomic mass of the middle element. When the elements are arranged in order to increase their atomic mass, the atomic mass of the middle element is approximately the arithmetic mean of the other two elements of the triad. He argues that the relative atomic mass of strontium is very close to the average age of the other two elements are similar to strantium, namely kalsiium and barium. Döbereiner f22raptor also revealed some other elements such groups. Salt-forming elements and their atomic masses, ie c1 = 35.5 Br = 80, I = 127 dsn. alkaline-forming elements and their atomic mass. Ie Li = 7, Na = 23And K = 39.
11.0
Arithmetic mean
Element
Of grouping these elements, there is an order. Every three nsur that are similar, atomic mass (A r) element f22raptor of the second (middle) f22raptor is the average atomic mass from the atomic mass of the first and third elements.
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Weakness Triad Classification A large number of the same element can not be grouped f22raptor into triads, for example, iron, manganese, nickel, cobalt, zinc and copper are similar elements but can not be placed in the triad. It may be that the elements are quite different can be grouped into triads. f22raptor Döbereiner can only classify 3 successful triad (highlighted in the table).
Because he failed to arrange the elements came to be known in the form of triads attempt at classification was not very successful. Although the ideas presented by Döbereiner next fall (to no avail), f22raptor but it is the first effort made in classifying elements.
In 1866, John AR Newlands British chemist suggests that the elements are arranged in order of atomic mass increases have properties that will be repeated every eighth element. That is, the first element is similar to the eighth element, the second element is similar to the ninth, and so on.
Periodicity properties of the elements in order of atomic mass increases every multiple of eight so-called law of octaves. At that time, the newly discovered f22raptor 60 elements. The noble gases are not included in the grouping system for undiscovered octaves.
Rb
Ce / La
In / Mo
Some elements are placed not sort by mass and there are two elements that are placed in the same column as the similarity properties. Newlands law of octaves was only valid for light elements. If passed, the similarity properties teryata too forced. For example, Ti possessed properties quite different from Al and B.
The weakness of this theory is in fact still in found several octaves which contains more than eight elements. Penggolonganya and is not suitable for atomic mass elements f22raptor is very large.
In 1869, Dmitri Ivanovich Mendeleev Russian chemist nationals compose 65 elements known at that time. Mendeleev sort the elements by atomic mass increases and chemical properties.
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