hafnium hf lenvironnement

    Technetium,  · Technetium is a chemical element with the symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive; none are stable, excluding the fully ionized state of 97 Tc. Nearly all technetium is produced as a synthetic element, and only about 18,000 tons can be found at any given time in the Earth's crust.. Naturally occurring technetium is a spontaneous fission ...