Audrey Lee's answer to r1yahzz's Secondary 3 Chemistry Singapore question.

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Audrey Lee
Audrey Lee's answer
37 answers (Tutor Details)
1st
Hello! To calculate Mr, we use the mass number of the atom in the periodic table. Mass number is the number on top of the atom in the periodic table. For example, mass number of sodium is 23 (you can refer to your periodic table in textbook, or google).