The atomic masses of elements are generally not whole numbers. Explain why.
the atomic masses of elements are the average weight of all its isotopes
The atomic masses of elements are generally not whole numbers because they are calculated based on the average mass of the isotopes of an element. Isotopes are different forms of an element that have the same number of protons but different numbers of neutrons in their nuclei.
Natural elements can have multiple isotopes, each with a different mass. The abundance of these isotopes, meaning the percentage of each isotope in a naturally occurring sample of an element, varies. Therefore, atomic masses are calculated by taking into account both the mass and abundance of each isotope.
The atomic mass of an element is calculated using the average of the masses of all the naturally occurring isotopes, weighted according to their abundance. Since the abundance of isotopes is not always exactly a whole number, the resulting atomic masses are often fractional or decimal values.
For example, let's consider carbon. It has three naturally occurring isotopes: carbon-12, carbon-13, and carbon-14. Carbon-12 is the most abundant isotope, making up around 98.9% of all carbon atoms. Carbon-13 has an abundance of only about 1.1%, and carbon-14 is present in trace amounts. The atomic mass of carbon is calculated by multiplying the mass of each isotope by its abundance and then adding them together. This calculation results in an atomic mass of approximately 12.01, which is not a whole number.
In summary, the atomic masses of elements are not whole numbers because they are calculated based on the average mass and abundance of their isotopes.