How can I identify atom from element? Also question about isotopes?!?

C12 is an element or an atom? If it is an element that is as an isotope, so the periodic table lists out elements instead of atoms? In the book "Biology" I am using to study, it says: "...For example, the symbol H (that is in the periodic table) means hydrogen atom, the symbol Rn (also in the... show more C12 is an element or an atom? If it is an element that is as an isotope, so the periodic table lists out elements instead of atoms? In the book "Biology" I am using to study, it says: "...For example, the symbol H (that is in the periodic table) means hydrogen atom, the symbol Rn (also in the periodic table) stands for radon, and the symbol Na is used for a sodium atom." This makes it confusing... How can I identify atom from element? Because I thought those are in the periodic table making them elements instead of atoms?? Sorry, I am a complete beginner at Chemistry!

Isotopes are the atoms containing the same # of protons (atomic #) and different # of neutrons (mass #). Isotopes should be compared with different atoms of the same element. Does this mean that I can use other elements other than carbon? because I only had that as an example: C12, C13, C14. The last two are not in the periodic table? Anyway, can I use nitrogen as an isotope or any other element and it just has to be the same element to have the same # of protons? Does this make all elements in the periodic table considered to be isotopes?
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