August 2018 NY Regents Chemistry Exam
32 Which electron configuration represents the electrons of an atom in an excited state?
(1) 2-5
(2) 2-8-5
(3) 2-5-1
(4) 2-6
Solution: In an atom the first shell can hold a maximum of 2 electrons, the second shell holds a maximum of 8 and the third holds a maximum of 8. Electrons in an excited state have moved from lower energy level to the higher energy level. We can see that in 2-5-1 electron configuration, an electron moved from the second energy level to the third. Otherwise, we would see 2-6 since the second energy level has a maximum of 8 electrons.
Answer: 3
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