The atomic mass of a chlorine atom is approximately 35.5 atomic mass units (amu).
This value represents the weighted average mass of all naturally occurring isotopes of chlorine, based on their relative abundance.
Why is the Atomic Mass of a Chlorine Atom not a Whole Number?
Chlorine’s atomic mass is not a whole number because it is derived from the average of its two main isotopes:
- Chlorine-35: Makes up about 75.78% of chlorine atoms in nature.
- Chlorine-37: Accounts for roughly 24.22% of chlorine atoms.
The weighted average of these isotopes gives chlorine its atomic mass of approximately 35.453 amu.
Key Facts About Chlorine’s Atomic Mass:
- Molar Mass: One mole of chlorine atoms weighs 35.453 grams.
- Isotopic Contribution: The value reflects both Chlorine-35 and Chlorine-37 in their natural abundance.
This value is essential for calculations in chemistry, such as determining the molar mass of compounds containing chlorine.
