Question

Do different atomic numbers, `Z`, specify different elements? How are isotopes differentiated?

Answer 1

My word yes.....

Explanation:

We differentiate elements by their atomic number, `Z`, which is the number of massive, positively charged particles in their nuclei... If there are the same number of protons we gots the same element.

On the other hand, a given element may contain variable numbers of neutrons, which are massive nuclear particles of ZERO charge. Protons and neutrons, at nuclear ranges, engage in the strong nuclear force, which binds the nucleus together, and is demonstrably stronger than the electrostatic force.

A nucleus may contain VARIABLE numbers of neutrons, and this gives rise to the phenomenon of isotopes...

And isotopes are best illustrated by their occurrence in the simplest element, hydrogen. All hydrogen nuclei contain ONE nuclear proton, i.e. `Z=1`; most hydrogen nuclei CONTAIN only this proton to give the protium isotope, `""^1H`; a few hydrogen nuclei contain ONE neutron, to give the deuterium isotope, `""^2H`; and fewer hydrogen nuclei still contain TWO neutrons to give the tritium isotope, `""^3H`. Such isotopes are very useful in so-called labelling experiments, and also given that the isotopes are fairly cheap.