Protactinium

Protactinium was identified in 1913 by Kasimir Fajans and Oswald Helmuth Göhring (who found a short-lived isotope) and then more completely in 1917 by Otto Hahn and Lise Meitner, along with Frederick Soddy and John Cranston. The name means 'before actinium' because protactinium-231 decays into actinium-227. It is one of the rarest and most expensive naturally occurring elements.

Protactinium is intensely radioactive, highly toxic, and extremely difficult to work with. In 1961, the UK Atomic Energy Authority processed 60 tons of nuclear waste to extract just 125 grams of protactinium for research. The element has virtually no commercial uses — it is primarily of interest to nuclear physicists studying radioactive decay chains. Its scarcity and danger make it one of the least-studied elements.

Protactinium's symbol 'Pa' is a great two-letter element for Spellement. It matches the start of words like 'park,' 'part,' and 'page,' fitting a very common English letter pair. This makes protactinium one of the most naturally useful elements for creative word building, despite the element itself being rarely encountered.