Atomic numbers and atomic mass numbers are always whole numbers because they represent the count of fundamental particles within an atom, which are indivisible and discrete entities.
Atomic Number (Z): The atomic number of an element represents the number of protons in the nucleus of an atom. Protons are fundamental particles with a positive charge. Since protons cannot be divided into smaller units, the count of protons in an atom is always a whole number. For example, hydrogen (H) has an atomic number of 1, indicating it has one proton.
Atomic Mass Number (A): The atomic mass number represents the total count of protons and neutrons in an atom's nucleus. Both protons and neutrons have a mass of approximately 1 atomic mass unit (u), and they are also indivisible. Thus, the sum of protons and neutrons is always a whole number. For example, carbon (C) has an atomic mass number of 12, indicating it has six protons and six neutrons.
It's worth noting that the mass of electrons is much smaller compared to protons and neutrons, and it is often neglected when determining the atomic mass number. Electrons do not significantly contribute to the overall mass of an atom.
In summary, atomic numbers and atomic mass numbers are whole numbers because they represent the count of indivisible particles (protons and neutrons) within an atom.