Answer:
The answer to your question is: 5 neutrons
Explanation:
Beryllium has 4 protons
# of neutrons in beryllium-9
Atomic number (Z) = 4 (number of protons)
Mass number (A) = 9 (number of protons + neutrons)
Mass number = number of protons + number of neutrons
9 = 4 + number of neutrons
neutrons = 9 - 4
neutrons = 5
