Make a Li atom with a mass number of 7. How many electrons did you place in the outermost orbital (ring)?

A lithium atom has 3 protons, so a neutral atom has 3 electrons. The mass number 7 changes the number of neutrons, not electrons; lithium’s electrons are arranged 2 in the first ring and 1 in the outermost ring, so the correct choice is 1.

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