The atomic weight of an element, also known as the atomic mass, is a weighted average of the masses of all naturally occurring isotopes of that element. The atomic weight of an element can vary slightly depending on the isotopic abundances found in nature.
For chlorine (symbol Cl), there are two naturally occurring isotopes: chlorine-35 and chlorine-37. The atomic weight of chlorine is calculated as the weighted average of the masses of these isotopes, taking into account their relative abundances.
The atomic weight of chlorine is approximately 35.45 atomic mass units (amu). This value represents the average mass of chlorine atoms found in nature, accounting for the proportions of chlorine-35 and chlorine-37 isotopes.
It's worth noting that the atomic weight of an element can be subject to slight variations as the isotopic abundances may vary in different sources or due to isotopic enrichment techniques.