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Describe Mende\'elevs periodic table. |
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Answer» \tMendeleev used atomic weight as the basis of classification of elements in the periodic table.He arranged 63 elements known at that time in the periodic table on the basis of the order of their increasing atomic weights and he placed elements with similar nature in same group.\tIn Mendeleev table, the elements were arranged in vertical columns, and horizontal rows. The vertical columns were called groups and the horizontal rows were called periods.\tThere were in all eight groups. Group I to VIII. The group numbers were indicated by Roman numerals. Group VIII occupy three triads of the elements each i.e. in all nine elements.\tThere were seven periods to accommodate more elements the period 4, 5, 6 and 7 were divided into two halves. The first half of the elements were placed in the upper left corner and the second half in the lower right corner of each box. Mendeleev’s Periodic Table : When elements are arranged in the order of increasing atomic masses, the element with similar properties occur at regular intervals. The properties of elements are a periodic function of their atomic masses.Mendeleev’s periodic table is based on the chemical properties of elements. It contains 6 periods (horizontal rows) and 8 groups (vertical columns).? Please elaborate in simple way... Mendeleev arranged all the known elements (63 at that time) in horizontal rows and vertical\xa0columns in order of increasing atomic masses in the form of table known as Periodic table. Mendeleev’s table has few vertical columns called groups and a few horizontal rows called periods. Mendeleev left certain gaps in his table and predicted that new elements would be discovered to fill up the gaps.The Mendeleev\'s modified periodic table consists of:(i) Nine vertical columns called groups. These are numbered from I to VIII and zero (The members of the zero group were not discovered at the time of Mendeleev). Each group from I to VII, is further sub-divided into two sub-groups-A and B. Group VIII consists of three sets, each containing three elements. Group zero consists of noble gases.(ii) Seven horizontal rows are called periods. These are numbered from I to VII. First period contains two elements, second and third periods contain eight elements each. These periods are called short periods. Fourth and fifth periods contain eighteen elements each. These periods are called long periods. Sixth period contains thirty two elements and is called longest period. Seventh period is incomplete and contains nineteen elements (At. No. 87-105). |
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