What were the criteria used by Mendeleev in creating his Periodic Tabl

1.	What were the criteria used by Mendeleev in creating his Periodic Table?
Answer» Solution :When Mendeleev started his work, 63 elements were known. He tried PUTTING the elements in orderof their atomic masses. He also examined the relationship between the atomic masses of the elements and their physical and chemical properties. Among chemical properties, Mendeleev concentrated on the compounds formed by elements with oxygen and hydrogen. He SELECTED hydrogen and oxygen as they are very reactive and formed compounds with most elements. The formulae of the oxides and hydrides formed by an ELEMENT were treated as one of the basic properties of an element for its classification. He then took 63 CARDS and on each card he wrote down the properties of one element. He selected out the elements with similar properties and pinned the cards together on a wall. He observed that most of the elements got a PLACE in a PeriodicTable and were arranged in the order of their increasing atomic masses.

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