Final answer:
The mass of a single atom of oxygen is approximately 2.66 × 10−23 grams, using the atomic mass unit based on carbon-12 as a reference, and measured with a mass spectrometer.
Step-by-step explanation:
The mass in grams of a single atom of oxygen can be calculated using the concepts of atomic mass units (amu) and Avogadro's number. A modern device called a mass spectrometer is used to measure the mass of atoms. The reference standard for atomic mass units is the carbon-12 nuclide, wherein one atom of carbon-12 is assigned a mass of 12 amu. An atomic mass unit is defined as a mass equal to one twelfth the mass of an atom of carbon-12. Since the atomic mass of an oxygen-16 atom is 16.00 amu, and by definition the molar mass of an oxygen atom is 16.00 g/mol, we can calculate the mass of a single atom.
An atom of oxygen-16 has a mass of approximately 2.66 × 10−23 grams (g). The atomic mass of individual atoms is not a whole number because it represents an average of the masses of all isotopes of the element that exist naturally, to reflect their relative abundance.