Neptunium and plutonium are two of the three elements named after planets. What is the third?

Along with the clavicle, which bone meets the humerus at the shoulder? Along with the Irish and the English setter, which breed, named after a Scottish duke, completes the best-known trio of… Along with Bach and Beethoven, which composer completes the "Three B's" of classical music? Besides the United States and Guatemala, which country borders Mexico? Along with crocodiles and alligators, which long-snouted reptiles make up the third family of the order Crocodylia? St. Croix and St. John are two of the three main U.S. Virgin Islands. What is the third? Which of these men was one of Noah's three sons who were aboard the ark? In September 1994, Jimmy Carter, Senator Sam Nunn and which retired general went to Haiti to negotiate a settlement wit…