MCQ
Mendeleev classified elements in :
- AIncreasing order of atomic groups.
- ✓Seven periods and eight groups.
- CSeven periods and nine groups
- DEight periods and seven groups.
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$CH \equiv CH\xrightarrow[{{\text{(2) CO , HCl , AlC}}{{\text{l}}_3}}]{{{\text{(1) Red hot Fe tube, 873 K}}}}$ Product The number of $sp ^{2}$ hybridized carbon atom(s) present in the product is ..........