Across a period from left to right, the atomic radius generally
Answer and explanation
Correct answer: C. decreases
- Step 1: Moving across a period from left to right, additional protons are added to the nucleus, increasing the nuclear charge .
- Step 2: The added electrons enter the same principal energy level without adding substantial shielding.
- Step 3: The stronger electrostatic pull of the nucleus contracts the electron cloud closer, causing the atomic radius to decrease.
Answer
decreases.
Why not the others: Increases contradicts the increasing effective nuclear charge across a period; stays the same ignores nuclear pull on the same valence shell; first increases then decreases is not the periodic trend.
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