1. 1. Mendeléev observed that most of the elements got a place in a Periodic Table and were arranged in the order of their increasing atomic masses. 2. It was also observed that there occurs a periodic recurrence of elements with similar physical and chemical properties.

    1. Mendeléev observed that most of the elements got a place in a Periodic Table and were arranged in the order of their increasing atomic masses.
    2. It was also observed that there occurs a periodic recurrence of elements with similar physical and chemical properties.

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