Question

Statement 1: Mendeleev left some gaps in his periodic table for the elements not discovered back then.​
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Statement 2: The position of hydrogen was specified in the Mendeleev’s periodic table.​

• A. Only statement 2 is correct.
• B. Both statements are correct.
• C. Both statements are incorrect.
• D. Only statement 1 is correct.

Answer 1

The correct option is D Only statement 1 is correct.

• Mendeleev left gaps in his periodic table because the properties of known elements predicted other, as-yet-undiscovered, elements in these locations.
• As Mendeleev organized his periodic table, he recognized that these gaps would be filled as future scientists identified new elements.
• Hydrogen possessed characteristics that resemble both the alkali metals and the halogens. So, it was placed above both the groups and could not be given a fixed position in Mendeleev's Periodic Table.