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MCAT Chemistry Question — Electron Configuration

What is the electron configuration of calcium in CaCl2?

A) 1s22s22p63s23p5

B) 1s22s22p63s23p6

C) 1s22s22p63s23p64s1

D) 1s22s22p63s23p64s2





This question asks the examinee to determine the electron configuration of the calcium ion, as it exists in calcium chloride. Calcium in its elemental state has a total of 20 electrons. Therefore Ca2+ has a total of 18 electrons. In the answer choices provided, choice B is the only electron configuration that contains 18 electrons making B the correct answer.

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