Carbon nuclides have different nucleon numbers but the same proton number.A nuclide is a specific __ of an square 1. The most common isotopes of carbon are Carbon -12 and Carbon -13

## Step1:The phrase "Carbon nuclides have different nucleon numbers but the same proton number" is just a different way to say that the atomic number of all carbon nuclides is same (since they all contain the same number of protons) while the nucleon number (equal to sum of protons and neutrons, commonly known as atomic mass) is different. Such different forms of the same element are referred to as isotopes.## Step2:We are supposed to fill out two terms here. The first term represents the specific count of nucleons (protons and neutrons) an atom or an ion contains, while the second term represents the fact that such a number does not change the basic character of an atom. From this it follows that we are talking about the "specific atomic mass" and "an element".### ###