Teacher:Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
Teacher: Now, understand the problem? Solve this instance: Adding the number of protons plus the number of neutrons in an atom decides its approximate mass; atomic number is another word for this value.
Student:
Adding the number of protons plus the number of neutrons in an atom, decides it's approximate mass, what is another word for this value?