Question

List any three observations which posed a challenge to Mandeleev's periodic table ...
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Answer 1

Observations that posed challenges to Mendeleev 's periodic table -

1) Position of Hydrogen

2) Position of Isotopes.

3) Irregular increase of atomic mass mentioned.

hope this will work.

Answer 2

Answer:

The observations which posed a challenge to Mendeleev periodic table are ; - Position of hydrogen in the first group among metal though it is non-metal. - Placing the elements with higher Atomic mass before the elements with lower Atomic mass. - No places were left in between two groups for isotopes.

Explanation:

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