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SAT 2 Chemistry Question

THAIDUYBINHTHAIDUYBINH Registered User Posts: 80 Junior Member
Sparknotes has 2 questions like this and I can't get the answers and explanations.

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

(A) S, Cl, F
(B) Cl, F, S
(C) F, S, Cl
(D) F, Cl, S
(E) S, F, Cl

Here is the key and explanation from Sparknotes:

Remember, atomic radii decrease moving across a period from left to right. This is because protons are added to the nucleus and these protons attract the electrons more strongly, pulling them in tighter and decreasing the atomic radius. Atomic radius increases moving down a group or family, however, because the value of n increases as you add another shell, the electrons spend more time away from the nucleus, dissipating the attraction between nuclear protons and themselves. Since fluorine and chlorine are both in the same group but chlorine is below fluorine, we know that chlorine is bigger than fluorine. Sulfur is to the left of both chlorine and fluorine, so it must be the smallest of all. Arranged in order of increasing size, they are S, F, Cl, or answer E.

However, if the atomic radii decrease moving across a period from left to right, S is bigger than Cl ( because S is to the left of Cl)

2. T or F ?
Oxygen has a smaller first ionization energy than fluorine. BECAUSE Oxygen has a higher Zeff value than does fluorine.
I think the answer should be T F but the answer from Sparknotes is F F.
Anyone can help me ?
Post edited by THAIDUYBINH on

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