Carbon-12 Is the Most Common Isotope of Carbon, and Has

question 77

Multiple Choice

Carbon-12 is the most common isotope of carbon, and has an atomic mass of 12 daltons. A mole of carbon in naturally occurring coal, however, weighs slightly more than 12 grams. Why?

• A) The atomic mass does not include the mass of electrons.
• B) Some carbon atoms in nature have an extra proton.
• C) Some carbon atoms in nature have more neutrons.
• D) Some carbon atoms in nature have a different valence electron distribution.
• E) Some carbon atoms in nature have undergone radioactive decay.

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