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Electronic configuration of M2+ ion is 2, 8, 14 and its atomic mass is 56 amu. The number of neutrons in its nucleus are:

Correct answer: A. 30

  • A. 30
  • B. 32
  • C. 42
  • D. 52

Explanation

Total number of electrons in M2+ ions are 2+8+14=24, since they lost two electrons to become this ion that means neutral M will have 26 electrons. Since neutral atoms have the same numbers of electrons and protons so the number of protons in M is also 26. As the question states that the mass number of M2+ is 56. Mass number, being the sum of protons and neutrons, can be used to calculate neutrons, by subtracting protons from it(56-26=30)

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