Definition of the word atomic mass

The term "atomic mass" refers to the mass of a single atom, expressed in atomic mass units (u). In the late 19th century, scientists discovered that the mass of an atom is not a whole number, but rather a fractional value. In 1913, chemist Aston proposed the concept of atomic mass based on measurements of the masses of different isotopes of an element using a mass spectrometer. He measured the mass-to-charge ratio of ionized particles in a magnetic and electric field, allowing him to distinguish between different isotopes and determine their relative masses. In 1929, chemist Frederic Joliot proposed that the atomic mass unit be defined as exactly 1/12th of the mass of an atom of carbon-12, the most abundant isotope of carbon. The concept of atomic mass has since played a crucial role in many areas of science, particularly chemistry and physics. By understanding the mass of individual atoms, scientists are able to calculate the properties and behavior of materials at the molecular level, which has led to significant advances in fields such as materials science, medicine, and technology.