Answer:
See explanation.
Step-by-step explanation:
The element corresponding to the atomic number 2 is Helium, which has a mass of 4.002602 u.
The number of neutrons would be calculated by solving the following equation:
mass number = protons + neutrons
This question is confusing because Helium doesn't have 24 protons. However, if the atomic number was 24 (Chromium) it would have 24 protons.
I'll provide an answer assuming you meant Chromium instead of Helium (but note that the process is the same to solve for the number of neutrons for either element).
Step 1: Determine Mass Number
Look this up on the periodic table. The mass number for Chromium is 51.9961 u which will be considered approximately 52 u for this problem.
Step 2: Solve
52 = 24 + # of neutrons
# of neutrons = 52-24 = 28
There are 28 neutrons in Chromium if it has 24 protons.