Chemistry - PERIODIC TABLE Question with Solution | TestHub

On moving down in a group atomic radii increases due to successive addition of extra shell hence $$\mathrm{O}<\mathrm{S}<\text{ Se }$$ Further As is in group 15 having one less electron in its $p$ orbital hence have higher atomic radii than group 16 elements. i.e., $\mathrm{O}<\mathrm{S}<\mathrm{Se}<\mathrm{As}$