I made a presentation about the periodic table, focusing solely on the atomic mass and the atomic number.

I mentioned Mendeleev's periodic law of sorting the elements out by their atomic masses from least to greatest all while putting the elements with the same characteristics on the same column. Is it okay if I say that we still follow mendeleev's methods however instead of using the atomic mass, we use the atomic number?

Question

I made a presentation about the periodic table, focusing solely on the atomic mass and the atomic number. 

I mentioned Mendeleev's periodic law of sorting the elements out by their atomic masses from least to greatest all while putting the elements with the same characteristics on the same column. Is it okay if I say that we still follow mendeleev's methods however instead of using the atomic mass, we use the atomic number?

vheah · Answer

My reasoning was because of the existence of isotopes which is why we dont use the atomic mass anymore, because isotopes can have the same atomic mass as other elements, while atomic number (or the number of protons in an element) strictly identifies a specific element uniquely.

hannansm · Answer

I think that's fine. However you may also want to not take any chances and mention decay to your audience and how it might change the number of protons in an element.