Question

Atomic size of sulphur is bigger then that of oxygen
Scientific Reason?

Answer 1

Fair question. The best answer is...there's more stuff in it. Oxygen has 8 Neutrons, 8 protons and 8 electrons.

Sulphur has 16 Neutrons, 16 protons and 8 electrons.

So the nucleus (Neutrons and protons) is bigger in sulphur. Just like a bunch of 32 balloons is bigger than a bunch of 16 balloons.

So that makes sense, but the big difference is in the electron configuration.

Answer 2

. the outer orbitals of oxygen are located 
closer to the nucleus than those of sulphur