AP Chemistrymediummcq1 pt
Using the simple shielding model in which every inner-shell electron cancels one unit of nuclear charge, estimate the effective nuclear charge felt by a valence electron in fluorine (Z = 9).
A.+7
B.+9
C.+2
D.+5
Explanation
Core Concept
Fluorine is 1s² 2s² 2p⁵, so a valence electron stands behind only the two 1s core electrons. Nine protons minus two units of shielding leaves a net attraction of +7. Fellow valence electrons in the same shell shield poorly and are ignored in this first-order model.
Correct Answer
A+7
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