Questions: Conclusion In your own words, DEFINE atomic mass and describe how to calculate it. How is it different from mass number? Explain how carbon's mass is 12.0108 , yet its mass number is 12.

Solution Steps

Atomic mass is the weighted average mass of the atoms in a naturally occurring sample of an element, measured in atomic mass units (amu). It takes into account the relative abundances of each isotope of the element.

To calculate the atomic mass of an element, you multiply the mass of each isotope by its relative abundance (expressed as a decimal), and then sum these values. The formula is: \[ \text{Atomic Mass} = \sum (\text{isotope mass} \times \text{relative abundance}) \]

The mass number is the total number of protons and neutrons in the nucleus of a single atom of an isotope. It is always a whole number. Unlike atomic mass, the mass number does not account for isotopic distribution or relative abundance.

Carbon's atomic mass is 12.0108 amu because it is a weighted average of its isotopes, primarily carbon-12 and carbon-13, with carbon-12 being the most abundant. The mass number of carbon is 12 because it refers to the most common isotope, carbon-12, which has 6 protons and 6 neutrons.

Final Answer