[vheax]

I have a presentation that talked about The Periodic Table and mentioned Mendeleev's arrangement by arranging the elements through their atomic masses. I said his rows had least to greatest atomic mass, while his columns had elements that had the similar properties of one another. Is it okay if I said that to this day we still follow Mendeleev's idea except we now arrange it through an elements atomic number due to the existence of isotopes that makes elements have similar atomic masses with others?

[Arkcon]

That is correct.  It how the Periodic table grew into what it is today.

[Borek]

Is it okay if I said that to this day we still follow Mendeleev's idea except we now arrange it through an elements atomic number

Sure. Plus, we know a lot more about the principle underlying periodicity of the properties, so we understand why the Mendeleev was right.

[Enthalpy]

With the addendum that the table isn't periodic any more. It features some pairs of successive lines of identical length whose elements have similar properties.