Answer:
M-A=N
Step-by-step explanation:
M-A=N
Here is an example.
The equation above means that the atomic number (A) subtracted from the average atomic mass (M) equals the combined amount of neutrons and protons. Since we know that 35 17Cl is Chlorine (this is because Chlorine (Cl) is the 17th number on the periodic table and has the average atomic mass of 35), we can insert our data into the equation and end up with the following:
35-17=18.
From here, we can tell that we have a mix of neutrons and protons, with the total being 18. Since the atomic number is 17, we can reasonably assume that there are 17 protons and 1 neutron.
But we still need to find the number of electrons. Fortunately, the number of electrons is always equivilant to the number of protons and the atomic mass, so we know that the number of electrons is 17.
So, we have;
17 Protons
1 Neutron
17 Electrons