Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Problem:Passage: As you learned in Chapter 1 "Introduction to Chemistry", the mass number is the sum of the numbers of protons and neutrons present in the nucleus of an atom. The mass number is an integer that is approximately equal to the numerical value of the atomic mass. Although the mass number is unitless, it is assigned units called atomic mass. Answer: mass number
Solution:
What number is the sum of the numbers of protons and neutrons present in the nucleus of an atom?