I say Neptunium, you say Poseidonium...

I was amused, when looking at the Greek Periodical Table of Elements, to find that a couple of element names had been "Hellenised".

Specifically, "Cerium" is "Demetrium" and "Neptunium" is "Poseidonium".

That fits the way that planets, for example, are named; Greek uses the corresponding Greek god rather than the Latin one, so for example, the one with the big rings is not "Saturn" but rather "Kronos". (In order, they are, from memory, Hermes - Aphrodite - Earth (Gaia) - Ares - Zeus - Kronos - Uranus (Ouranos) - Poseidon. Pluto is just Pluto, though.)

So with the elements, we have the Neptune = Poseidon correspondence as well as Ceres = Demeter. (Compare also "cereals", which are "demetriacs" in Greek.)

I must admit I was a bit disappointed that Lawrencium is "Lorensio" rather than "Lavrendio". But it seems that the newer ones tend to be written phonetically (according to modern Greek pronunciation) rather than taking the spelling as the base.