[Galean]

I am new to chemistry and was wondering if someone could tell me why in some periodic tables the Atomic Number 110 differs.  Sometimes it is Uun (ununnilium) and other times it is Ds (darmstadtium) ?

[Jorriss]

When a new element is discovered it's given a temporary name, Uun in this case, and it is then, upon confirmation of it's existence and some other shenanigans, given an official name.

The periodic tables calling it Uun are just out of date most likely.

[Galean]

Thank you, that helps clear up some things.