the atomic number
This is not possible. The number of protons identifies an element, and all of the atoms of the same element have the same number of protons. The atoms of an element can, however, have different numbers of neutrons, and they are called isotopes.
An atom or element that have different masses are known as isotopes.
Isotopes of the same element have different numbers of neutrons and mass.
neutrons
Isotopes of the same element have different number of neutrons.
Isotopes are atoms of the same element that are only different by the number of neutrons they have
Two different isotopes of an element have different numbers of neutrons. That's what an isotope is. So, no, isotopes of an element can not have the same number of neutrons.
Isotopes of the same element have a different number of neutrons.
Atoms have isotopes: it is true, the isotopes of the same element have different number of neutrons.
If an atom of the same element has the same number of protons but a different number of neutrons, then they are isotopes.
Isotopes are atoms of an element having different number of electrons.
Isotopes have different masses, so the superscript preceding the symbol will be different. An example could be carbon with atomic mass 12 and carbon with atomic mass 14. 12C and 14C with the 12 and 14 being superscripts, identifies the different isotopes.