Final answer:
The atomic masses on the periodic table are not whole numbers because they are calculated based on the average mass of all the isotopes of an element.
Step-by-step explanation:
The atomic masses on the periodic table are not whole numbers because they are calculated based on the average mass of all the isotopes of an element. Isotopes are atoms of the same element that have a different number of neutrons, and each isotope has a different mass. The atomic mass is the weighted average of all the isotopes, taking into account their abundance in nature.
For example, carbon has two main isotopes: carbon-12 and carbon-13. Carbon-12 is the most abundant isotope, while carbon-13 is less common. The atomic mass of carbon is calculated by taking into account the mass of each isotope and its abundance, resulting in a value of approximately 12.01, which is not a whole number.
By using the average atomic mass, scientists can represent the most common isotopic form of an element with a whole number on the periodic table, known as the mass number. The mass number is the sum of the protons and neutrons in the nucleus of an atom.
Learn more about Atomic masses on the periodic table