Order the elements S, Cl, and F in terms of increasing atomic radii.

I thought the answer was F, S, Cl, but the answer key said it was S, F, CL

Why? AR decreases from left to right. Sulfur has one more energy level, so shouldn't its atomic radii be greater than fluorine?

1 answer

I think it is F smallest to Cl to S the largest which doesn't agree with your answer key. See the link below and look under calculated value. http://en.wikipedia.org/wiki/Atomic_radii_of_the_elements_(data_page)

Yes, AR decreases from left to right, which is why I think S is larger than Cl BUT F is not in the same period. AR ALSO decreases as we move UP in a column. Using your rationale, He should be larger than F (but it is smaller).