The pair that has similar atomic radii is :

An 'Assertion' and a 'Reason' are given below. Choose the correct answer from the following options :
Assertion (A) : Vinyl halides do not undergo nucleophilic substitution easily.
Reason (R) : Even though the intermediate carbocation is stabilized by loosely held p-electrons, the cleavage is difficult because of strong bonding.

What will be the major product when m-cresol is reacted with propargyl bromide (HC$$ \equiv $$C–CH₂Br) in presence of K₂CO₃ in acetone?

The coordination numbers of Co and Al in [Co(Cl)(en)₂]Cl and K₃[Al(C₂O₄)₃], respectively, are : (en = ethane-1, 2-diamine)