身近な科学
Why does the periodic table repeat patterns?
Across period 3, atomic size generally falls while first ionization energy generally rises, with instructive exceptions.
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短い答え
Across period 3, atomic size generally falls while first ionization energy generally rises, with instructive exceptions.
本当は何が起きている？
Sodium has 11 electrons; its outer 3s electron helps explain why sodium readily forms Na+.
役立つイメージ
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The repeating structure comes from electron configurations. As shells and subshells fill, similar valence-electron patterns recur, and chemical behaviour echoes those patterns.