eka-protactinium

Noun

 * 1) Unbitrium (Ubt), an unsynthesized chemical element with atomic number 123.
 * 2) Unquadunium (Uqu), an unsynthesized element with atomic number 141.

Usage notes
This inconsistency, between referring to element 123 versus element 141, comes from the fact the are not known, so it is unknown what element would be placed directly below protactinium.