Hafnium (symbol Hf, atomic number 72) is a metal with an enormous neutron-capture cross-section, used in reactor control rods. It is classified as a transition metal and sits in group 4, period 6 of the periodic table.
Overview
Hafnium is the chemical element with atomic number 72 and the symbol Hf. With a standard atomic weight of 178.49, it is a transition metal. In the periodic table it occupies group 4 and period 6, and under standard conditions it is normally a solid. Hafnium is a metal with an enormous neutron-capture cross-section, used in reactor control rods.
Atomic structure
An atom of Hafnium has 72 protons in its nucleus and, when neutral, 72 electrons arranged in the configuration [Xe] 4f14 5d2 6s2. Its standard atomic weight of 178.49 reflects the natural mix of its stable isotopes.
Discovery and place in the table
Hafnium was discovered in 1923 by Dirk Coster, George de Hevesy. It follows Lutetium (Lu) and precedes Tantalum (Ta) in order of atomic number.
| Atomic number | 72 |
|---|---|
| Symbol | Hf |
| Atomic mass | 178.49 |
| Category | Transition metal |
| Group | 4 |
| Period | 6 |
| Electron configuration | [Xe] 4f14 5d2 6s2 |
| Phase at STP | Solid |
| Discovered | 1923 (Dirk Coster, George de Hevesy) |