Question

How many neutrons does element X have if its atomic number is 22 and its mass number is 96?

Answer 1

1. The mass number is protons + neutrons = mass number. In this case, we have protons + neutron = 164.The atomic number is simply the number of protons so we have 43 + neutrons = 164. Subtracting 43 from both sides we get neutrons = 121.
2.  = 4

3. The number of protons in the nucleus does not equal the number of neutrons. 

A=mass number: 
Z=atomic number (= number of protons)
N=number of neutrons:

A=Z+N

If the number of protons in the nucleus is equal the number of neutrons , we would have an even mass number; because Z=N=x; then A=x+x=2x  (this is always an even number) but  23 is an odd number, therefore the number of protons in the nucleus does not equal the number of neutrons.