January 2018 NY Regents Chemistry Exam
32 Which electron configuration represents the electrons of an atom in an excited state?
(1) 2–2
(2) 2–2–1 (3) 2–8
(4) 2–8–1
Solution: When an electron is excited, it moves from a lower energy level to higher. The first energy level has a maximum of 2 electrons. The second energy level has a maximum of 8 electrons. The third energy level has a maximum of 8 electrons. If we look at choice 2, we see 2-2-1. This means 2 electrons in the first enegy level, 2 electrons in the second energy level and 1 in the third energy level. We know that the second level has a maximum of 8 electrons. Yet, it has only 2 electrons and another electron in the third level. This means that one of the electrons in the second level went up to the third level (got excited).
Answer: 2
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