I keep getting “Atomic radius trend” questions wrong in Periodic Table & Periodicity. What's the trap?
reversing the across-a-period trend.
The usual trap: reversing the across-a-period trend. How to avoid it: more protons but the same shell → electrons pulled in tighter across a period. Go back to the definition — atomic size decreases across a period (more nuclear pull) and increases down a group (new shells).
Key point
Atomic radius trend
Common mistake
reversing the across-a-period trend.
Memory tip
more protons but the same shell → electrons pulled in tighter across a period.
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