What element has the symbol 'Rf'?

The story behind the answer

Rf is Rutherfordium, element 104 on the periodic table. The other options have different symbols: Radon is Rn, Francium is Fr, and Rhenium is Re.

Rutherfordium is a synthetic, highly unstable transactinide named after Ernest Rutherford, the pioneer of nuclear physics. First created in the 1960s in heavy-ion experiments, its naming sparked a US–Soviet dispute that IUPAC settled in 1997 in favor of Rutherfordium (Rf). It sits in group 4 beneath hafnium and is predicted to share similar chemistry. Memory tip: Rf—“Rutherford Found the nucleus,” linking the symbol to the scientist’s landmark discovery.