According to the octet rule, what is true about the reactivity of halogens? a halogen atom has seven electrons in its valence shell, so halogens are very reactive. a halogen atom has two electrons in its valence shell, so halogens are very unreactive. a halogen atom has two electrons in its valence shell, so halogens are very reactive. a halogen atom has seven electrons in its valence shell, so halogens are very unreactive.

A halogen atom has seven electrons in its valence shell, so halogens are very reactive. (Option A)

Explanation: The elements in-group 7 are often referred as “halogens”.  When they form ions, they tend to gain an electron and form negative ions. They are all non-metals and their reactivity down the group decreases because the atomic radius increases in size (so fluorine is the most reactive halogen of group 7)

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