neptunium/nɛpˈtjuːniəm/EtymologyFrom Neptune + -ium, after the planet. The previous element is uranium, named after the previous planet: Uranus.neptunium means the transuranic chemical element with atomic number 93 and symbol Np. Lexicurio rates it Rare gem — a strength score of 83 out of 100.nounThe transuranic chemical element with atomic number 93 and symbol Np.