Periodic system shows grouping Elements. Attempts to classify the elements has been started since the experts (in the late 18th century) found more and more elements. The simplest grouping is to divide the elements into metals and nonmetals.
In 1829, Johan Wolfgang Dobereiner see any similarities between the nature of some elements, and classify the elements of nature according to similarity. Each group was composed of three elements, so-called Triade. If the elements in one Triade increase ordered by Atomic Mass, atomic mass and it attributes the second element is the average of the atomic mass / properties first and third elements. Dobereiner findings showed a relationship between atomic mass and properties of elements.
In 1864 a British chemist named AR Newlands announced the discovery of the so-called law of octaves. Newlands arrange the elements according to their Relative Atomic Mass increases. Proved the elements that differ 1 octave (element number 1 to number 8, element number 2 to number 9, and so on) show similarity properties. At Newlands octave compiled list, the elements of noble gases (He, Ne, Ar and so on) has not been found. Newlands octave law only applies to light elements (low Ar)
In 1869 the Russian scholar named Dmitri Ivanovich Mendeleev, based on observations of 63 elements known at that time, concluded that the properties of elements are periodic function of the relative atomic mass. That is, if the elements arranged according to their relative Atomic Mass Increases, the specific properties will be repeated periodically. Mendeleev create the periodic elements of a list drawn up according to their relative atomic mass increases. Elements that have characteristics in common are placed in vertical columns called groups. Mendeleev periodic list published in 1872. There are several weaknesses in the Mendeleev periodic system: first, the placement of some elements not to increase their relative atomic mass. For example, the placement of tellurium (Te) and iodine (I). Heavier tellurium (Ar = 128) preceding the lighter iodine (Ar = 127). This upside-down placement had made considering the similarity in the nature groups elements. Iodine more shows similarities with the nature of fluorine, chlorine and bromine, while tellurium more shows similarities with the nature of oxygen, sulfur and selenium.
second, there are still many unknown elements at the time, so in the table there are many empty places.
In 1914 Henry GJ Moseley discovered that the order of elements in the periodic table according to the increase in atomic number elements. Placement of tellurium and iodine are not in accordance with the relative atomic mass increases, the increase was in accordance with the atomic number. Tellurium has atomic number 52 while the 53 iodine. A periodic nature rather as a function of atomic number.
Modern periodic system, which is also called long-form periodic system, arranged according to the increase in atomic number and similarity of properties. Modern periodic system can be considered as improvements Mendeleev periodic system.
In 1829, Johan Wolfgang Dobereiner see any similarities between the nature of some elements, and classify the elements of nature according to similarity. Each group was composed of three elements, so-called Triade. If the elements in one Triade increase ordered by Atomic Mass, atomic mass and it attributes the second element is the average of the atomic mass / properties first and third elements. Dobereiner findings showed a relationship between atomic mass and properties of elements.
In 1864 a British chemist named AR Newlands announced the discovery of the so-called law of octaves. Newlands arrange the elements according to their Relative Atomic Mass increases. Proved the elements that differ 1 octave (element number 1 to number 8, element number 2 to number 9, and so on) show similarity properties. At Newlands octave compiled list, the elements of noble gases (He, Ne, Ar and so on) has not been found. Newlands octave law only applies to light elements (low Ar)
In 1869 the Russian scholar named Dmitri Ivanovich Mendeleev, based on observations of 63 elements known at that time, concluded that the properties of elements are periodic function of the relative atomic mass. That is, if the elements arranged according to their relative Atomic Mass Increases, the specific properties will be repeated periodically. Mendeleev create the periodic elements of a list drawn up according to their relative atomic mass increases. Elements that have characteristics in common are placed in vertical columns called groups. Mendeleev periodic list published in 1872. There are several weaknesses in the Mendeleev periodic system: first, the placement of some elements not to increase their relative atomic mass. For example, the placement of tellurium (Te) and iodine (I). Heavier tellurium (Ar = 128) preceding the lighter iodine (Ar = 127). This upside-down placement had made considering the similarity in the nature groups elements. Iodine more shows similarities with the nature of fluorine, chlorine and bromine, while tellurium more shows similarities with the nature of oxygen, sulfur and selenium.
second, there are still many unknown elements at the time, so in the table there are many empty places.
In 1914 Henry GJ Moseley discovered that the order of elements in the periodic table according to the increase in atomic number elements. Placement of tellurium and iodine are not in accordance with the relative atomic mass increases, the increase was in accordance with the atomic number. Tellurium has atomic number 52 while the 53 iodine. A periodic nature rather as a function of atomic number.
Modern periodic system, which is also called long-form periodic system, arranged according to the increase in atomic number and similarity of properties. Modern periodic system can be considered as improvements Mendeleev periodic system.
