Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
One example: Earth rotates on its axis once times in one day.
Solution is here: How many times does Earth rotate on its axis in one day?
Explanation: The given output correctly poses a question based on the scientific fact given.

Now, solve this: 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.
Solution:
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?