Alphabetically, which noble gas comes last?

Listed alphabetically by last name, which U.S. president comes last? Which continent's countries run alphabetically from Argentina to Venezuela? Alphabetically, which of Snow White's seven dwarfs comes first? Listed alphabetically by last name, which U.S. vice president comes first? Alphabetically, which planet in our solar system comes last? What is the alphanumeric name of the most popular of three audio encoding layers in an MPEG standard released in 1993? Which author, already a successful poet, began his career as a novelist in 1814 with a tale of the Highlands? Which German-born biochemist discovered the citric acid cycle of metabolism and energy production?