The numbers listed represent the number of electrons in the first, second, and third energy levels, respectively. On this basis, which of the following is an unstable or reactive atom?

Question

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An atom with incomplete outermost energy level is unstable and reactive. In option D, the atom has only 1 electron in its outermost energy level, making it unstable and reactive. Option A has a completely filled outermost energy level, making it the most stable and inert gas-like. Option B and C also have completely filled energy levels, making them stable and inert.

The Numbers Listed Represent the Number of Electrons in the First