Question

21. Why noble gases were not known earlier? (give two reasons)​

Answer 1

Because most elements were discovered through their reactivity with other elements, typically with oxygen, it was difficult for scientists to work with a substance that seemed to have little or no chemical properties based upon the lack of reactivity.

The common thing with the noble gases is that they have full outer shells, and don't react with any elements. Noble gases were discovered later than other elements , simply because they were extremely unreactive . Being intert they were difficult to isolate via chemical reactions .

Answer 2

Answer:

Noble gases were not known earlier because:

1)They are inert

2)It was found that their valency was 0