What element has the symbol 'Hf'?

The story behind the answer

‘Hf’ is the chemical symbol for hafnium (element 72), a silvery transition metal in group 4. Don’t confuse it with H (hydrogen), Ho (holmium), or Hs (hassium). Hafnium commonly occurs with zirconium and shares very similar chemistry, which is why it’s used in nuclear reactor control rods—hafnium strongly absorbs neutrons.

Discovered in 1923 in Copenhagen by Coster and Hevesy, its name comes from Hafnia, the Latin name for Copenhagen. Memory tip: Hf → HaFnia → HaFnium.