Final answer:
A randomly selected carbon atom is more likely to have a mass very close to 12 amu, which is the mass of the most common isotope, carbon-12, rather than the weighted average atomic mass of 12.011 amu.
Step-by-step explanation:
No, a carbon atom selected at random is not likely to have a mass of 12.011 amu. The atomic mass listed on the periodic table is a weighted average that takes into account the different isotopes of carbon and their natural abundance. Carbon mainly exists as two stable isotopes: carbon-12, which has a mass number of 12 and an atomic number of 6, and carbon-13, with a mass number of 13 and an atomic number of 6. The vast majority of carbon is carbon-12, which has a mass very close to 12 amu (12.00 amu), whereas carbon-13 has a mass of about 13.003355 amu.
When calculating the average atomic mass, both isotopes contribute to the final value. As given in the calculation, (0.9889 × 12 amu) + (0.0111 × 13.003355 amu) = 12.01 amu, which is relatively close to the exact average atomic mass of 12.011 amu indicated on the periodic table.
Therefore, any single carbon atom you pick is more likely to be close to the mass of the most abundant isotope, carbon-12, rather than the average atomic mass. In reality, only a small fraction of carbon atoms will have the higher mass corresponding to carbon-13, impacting the average.