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What are the merit and demerit of Mendel periodic table? |
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Answer» Demerits: ◆ the position of isotopes could not be explained and had not given separate places. for example the element chlorine has two isotopes CL 35 and CL 37, the placing of these two isotopes of chlorine having different masses in the same group of the periodic table could not be explained.◆ according to Mendeleev\'s periodic law the elements are arranged in the order of increasing atomic masses, so the element with low atomic mass should come first and the element with higher atomic mass should come later. His law could not explain the abnormal situation of wrong order of atomic masses. ◆ the electronic configuration of hydrogen resembles with alkali metals it combines with Nitrogen, Oxygen and sulphur to give similar type of compounds as given by alkali metal. But it is also exist in diatomic form and combines with metal and non metal to form covalent compound. Its position was not fixed in the Mendeleev periodic table but it was kept with alkali metal. It is Mendeleev\'s periodic table. Merits: ◆ Ha left proper gaps for the undiscovered elements like gallium scandium and Germanium. ◆The properties of then undiscovered elements were predicted. The predicted properties were found to be almost the same as actual property is when these elements were discovered later on. ◆The noble gases are placed in a separate group because they are chemically unreactive. |
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