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JAMB Chemistry 1981 Question 9

Question 9

Atomic Structure

The mass number of an atom is

  1. A.the number of electrons in the atom
  2. B.the number of protons in the nucleus of the atom
  3. C.the number of neutrons in the nucleus of the atom
  4. D.the sum of numbers of electrons and protons in the atom
  5. E.the sum of the numbers of protons and neutrons in the nucleus of the atom
Show the answer and explanation

Answer: E (the sum of the numbers of protons and neutrons in the nucleus of the atom)

Explanation

The mass number counts the particles in the nucleus: protons plus neutrons.