The two groups consisting of elements are a bit dubious. Specifically:
-Silver's name is not derived from a country. Argentina is named after Argentum, yes, but not the other way around.
-Americium is not not named after a country. It is named, I believe, after the Americas rather than any particularly constituent nation. So it could potentially fit into the 'larger than a country' group.
-What is the standard by which you are judging 'bigger than a country' for that group? Of course, Pluto and the Sun are both bigger than any terrestrial state. However, Scanadium is named after Scandinavia, which consists of countries but is not bigger than all other countries. It just creates a rather arbitrary way of defining size.