Question

Is there any method to find the atomic mass of an element if the number of neutrons are not known and only atomic number is given?

Answer 1

You find the atomic mass (AM) of an element by adding the neutrons (N) and the protons (P).
AM = P + N
If you are looking for the neutrons you can instead subtract the protons from the atomic mass:
N = AM - P
In the periodic table you will find the protons by looking at the atomic number at the top and the atomic mass will be found on the bottom.
Let’s say you are using Nitrogen, the atomic number is 7 therefore there are 7 protons. The atomic mass is 14
N = 14 - 7
N = 7 therefore there are 7 neutrons