Final answer:
An atomic mass unit (amu) is a unit of mass used to express atomic and molecular weights, equivalent to one-twelfth the mass of a carbon-12 atom, or approximately 1.660539 × 10^-24 grams.
Step-by-step explanation:
What is an Atomic Mass Unit (AMU)?
The atomic mass unit (amu) is a standard unit of mass that quantifies mass on an atomic or molecular scale. It is defined as one-twelfth the mass of a carbon-12 atom, which is an isotope of carbon with six protons and six neutrons in its nucleus. Since the mass of atoms are infinitesimally small, using grams to measure them is not practical. As a result, the amu is used instead to provide a more manageable value, allowing scientists to compare atomic masses with ease. One amu is equal to approximately 1.660539 × 10-24 grams.
For illustrative purposes, consider that the atomic mass of hydrogen, the lightest element, is about 1 amu, while the atomic mass of carbon-12 is exactly 12 amu. The use of amu makes it easier for chemists and physicists to work with and understand the relative scales of atomic masses. This unit is vital for a wide range of scientific calculations, including those involving the use of the mole concept in stoichiometry.