日常生活中的科学
Why are atoms different sizes?
A sodium atom is larger than a chlorine atom in the same period because effective nuclear attraction increases across the row.
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简短答案
A sodium atom is larger than a chlorine atom in the same period because effective nuclear attraction increases across the row.
真正发生了什么？
Across period 3, atomic size generally falls while first ionization energy generally rises, with instructive exceptions.
一个有用的直观图景
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Atomic size reflects a competition between nuclear attraction, electron shielding and which shells are occupied. That is why radius changes systematically—but not perfectly smoothly—across the periodic table.