Question

which has got larger atomic size, oxygen or chlorine and why?

Answer 1

chlorine because it has more number of electrons as compared to oxygen , As the subshell increases , Atomic size increases

Answer 2

We confirm this by looking at the atomic radius of oxygen and chlorine, seeing that oxygen is a smaller atom than chlorine, and thus that the force felt by the outermost electrons to the nucleus pull oxygen's electrons more chlosely than chlorine's.

Why is chlorine more reactive than oxygen?

chlorine has two atoms of small size and have high electronegativity difference which weakens there double bond i.e bond dissociation energy is less as compare to oxygen which has larger size and can distribute its electrons on more are and it also has double bond which make it more strong