The atomic numbers of elements in the periodic table are whole numbers because they represent the number of protons found in the nucleus of an atom. Each element has a unique atomic number, which determines its position in the periodic table and defines its chemical properties.
However, other atomic properties, such as atomic mass or the number of neutrons in the nucleus, may not always be whole numbers. This is because atomic mass takes into account the presence of different isotopes of an element. Isotopes are variants of an element that have the same number of protons but different numbers of neutrons.
The atomic mass listed for each element on the periodic table is usually a weighted average of the masses of its naturally occurring isotopes. Since the abundance of each isotope can vary, the atomic mass may not be a whole number. Instead, it is expressed with decimal values to account for the relative proportions of different isotopes.
For example, the atomic mass of carbon (C) is listed as approximately 12.01 on the periodic table. This value considers the presence of carbon-12, the most common isotope, along with a smaller proportion of carbon-13, which has an extra neutron. The weighted average of these isotopes leads to a decimal value for atomic mass.
In summary, while atomic numbers represent whole numbers, atomic masses may include decimal values due to the contributions of different isotopes with varying masses.