Apentix/AP Chemistry/Unit 1: Atomic Structure and Properties/Question

AP Chemistrymediummcq1 pt

Why does atomic radius decrease across a period from Li to F?

A.Effective nuclear charge increases while the shell stays n = 2

B.The number of shells decreases

C.Electronegativity decreases

D.More neutrons compress the nucleus

Explanation

Core Concept

Protons are added with each element, but the new electrons stay in the same shell, so shielding grows slowly. The rising Zₑff pulls the same-size shell inward.

Correct Answer

AEffective nuclear charge increases while the shell stays n = 2

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