Yes, an atom can have a higher atomic mass than its element due to the existence of isotopes. Isotopes are atoms of the same element that have different numbers of neutrons in their nuclei. Since the atomic mass of an atom is the sum of the masses of its protons, neutrons, and electrons (where electrons contribute very little to the overall mass), isotopes with varying numbers of neutrons will have different atomic masses.
Here are a few examples of isotopes where an atom has a higher atomic mass than the average atomic mass of its element:
Carbon: Carbon-14 (14C) is an isotope of carbon with a higher atomic mass compared to the more common carbon-12 (12C). Carbon-12 is the most abundant isotope of carbon, while carbon-14 is a radioactive isotope used in carbon dating.
Hydrogen: Deuterium, also known as heavy hydrogen, is an isotope of hydrogen with one neutron in its nucleus. It has a higher atomic mass than the most common isotope of hydrogen, protium (which has no neutrons).
Oxygen: Oxygen-18 (18O) is an isotope of oxygen that has a higher atomic mass compared to the more abundant oxygen-16 (16O). Oxygen-18 is used in various scientific and medical applications, including isotope labeling and studying metabolic processes.
These examples illustrate how isotopes can have different atomic masses within the same element, offering variations in the number of neutrons in the atom's nucleus.