Why are you people deleting my question?
How is the Atomic mass of chlorine is 35.5u . As Atomic mass is sum of no. of protons and no. of neutrons.

Dear Student
There are two isotopes of chlorine is present, i.e., Cl-35 and Cl-37
Abundance of Cl-35 is around 75% and of Cl-37 is around 25%.
So, the average atomic mass of Cl is 35.5
This concept of finding average atomic mass, you will study in higher classes.
Regards

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I think because some student are chatting while answering questions or asking questions.
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