What element has the symbol 'Rg'?

The story behind the answer

Rg is the symbol for Roentgenium (element 111), named in honor of Wilhelm Conrad Röntgen, discoverer of X-rays. The other options have distinct symbols: Rhodium is Rh, Rubidium is Rb, and Ruthenium is Ru—so only Roentgenium fits Rg.

Roentgenium is a synthetic, superheavy element made in particle accelerators and decays almost instantly, so it’s used mainly for research. Memory tip: think “Röntgen → X-rays → Radiography → Rg.” Linking Rg to Röntgen helps distinguish it from the similar-looking Rh, Rb, and Ru.