Question

9.
Which of the following had not been
discovered by the time when
Mendeleev published his periodic
table ?
(1) Actinides
(2) Halogens
(3) Lanthanides
(4) Noble gases​

Answer 1

Answer:

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Answer 2

The noble gases are not discovered at the time when Mendeleev discovered his periodic table.

Option: (4)

Explanation:

• Mendeleev discovered the best form of the periodic table in which he gave new places for the lanthanides and actinides series.

• In addition to this year also predicted some of the elements like gallium.

• However he could not discoverthe noble gases.

• This is because the noble gases are inactive and hence they do not react with other elements to form compounds.

• In addition to this one of the noble gases existed till that date and hence he did not respect that noble gases could be present.

To know more about the noble gases,

What are noble gases ?arrange them in proper order

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