The relative atomic mass of an element is

  • A. the mass in grams of one atom of the element
  • B. the average mass of its atoms compared with one twelfth the mass of a carbon 12 atom
  • C. the number of protons in its nucleus
  • D. always a whole number

Explanation

Relative atomic mass is a ratio, so it has no units, and it is an average weighted by the natural abundance of the isotopes. That averaging is why chlorine is quoted as 35.5 rather than as a whole number, since it is a mixture of chlorine 35 and chlorine 37. The number of protons is the atomic number, an entirely different quantity.

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