Question

Beryllium has a nucleus composed of protons and neutrons. Given the data, how many neutrons are in a typical Beryllium nucleus?
A) 3
B) 4
C) 5
D) 9

Answer 1

Beryllium has a mass number of 9 and 4 protons.  To find the number of neutrons you need to subtract the number of protons from the mass number.  so...
neutrons = mass - # protons
neutrons = 9 - 4 = 5

Answer 2

I believe the answer is C