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A dense, radioactive, noble gas is ____.
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bromine (Br)
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Lighter-than-air party balloons are filled with ____.
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gold (Au)
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A toxic, reddish-brown liquid halogen is ____.
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helium (He)
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The lightest and most abundant element in the Universe is ____.
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hydrogen (H)
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Common oxidation states for carbon (C) and ____ are -4 and +4.
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nitrogen (N)
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About 78% of the Earth's atmosphere is ____.
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potassium (K)
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The most malleable and ductile metal element is ____.
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radon (Rn)
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Li, Na, and ____ are highly reactive alkali metals.
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silicon (Si)
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