Classification of nuclides is as follows:
Isotopes: ; has the same atomic number but, different mass number.
Isobars ; has the same mass number but, different atomic number.
Isotones: ; has same neutron number but, different proton number.
Now,
Radius of nucleus, ...(i)
where, is the range of nuclear force (or Nuclear Unit Radius)
Density is given by, ...(ii)
But, ...(iii)
From (i) and (iii), we get
where,
...(iv)
From (ii) and (iv), we have
Thus, we can see that nuclear density is clearly independent of mass number A.
We have,
Rate of increase of element =
That is,
The solution to this is the sum of the homogeneous solution,
where c is a constant, and
a particular solution,
Therefore, the required solution is,
The constant c is obtained from the requirement that the initial number of nuclei be zero,
so that,
The equilibrium value is
Setting N equal to 1/2 of this value gives,
The result is independent of R.