Atomic weight, also known as atomic mass, is a property of an atom that represents the average mass of its isotopes. Isotopes are atoms of the same element that have different numbers of neutrons in their nuclei, resulting in different atomic masses.
The atomic weight is typically expressed in atomic mass units (amu). It is calculated by taking into account the mass of each isotope of an element and its relative abundance in nature. The atomic weight is a weighted average of the masses of the isotopes, where the weighting factor is the relative abundance of each isotope.
For example, carbon has several isotopes, including carbon-12, carbon-13, and carbon-14. Carbon-12 is the most abundant isotope, followed by carbon-13 and carbon-14. The atomic weight of carbon is approximately 12.01 amu, which takes into account the masses and abundances of these isotopes.
Atomic weights are important in various scientific fields, particularly in chemistry and physics, as they are used to calculate stoichiometry, determine molecular weights, and understand the behavior of elements in chemical reactions. The values of atomic weights are listed on the periodic table of elements, and they provide a useful reference for studying and understanding the properties of different elements.