Hafnium (Hf)
Element 72 · Transition metal · atomic mass 178.49 u · group 4, period 6
Electron shells: 2, 8, 18, 32, 10, 2
Hafnium is chemically almost a twin of zirconium but behaves in the exact opposite way toward neutrons — it soaks them up. That single difference decides which one goes in a control rod.
Hafnium oxide let chip makers keep shrinking transistors when silicon dioxide stopped insulating well enough.
- Atomic number
- 72
- Atomic mass
- 178.49 u
- Electron configuration
- [Xe] 6s² 4f¹⁴ 5d²
- Group · period · block
- 4 · 6 · d
- Oxidation states
- +4
- Electronegativity
- 1.3 (Pauling)
- Melting point
- 2,233 °C
- Boiling point
- 4,603 °C
- Density
- 13.3 g/cm³
- State at 20 °C
- Solid
- Appearance
- Silvery, lustrous metal
- Discovered
- Dirk Coster and George de Hevesy, 1923
72 protons, and 72 electrons when neutral
IUPAC standard atomic weight
Titanium group
What Hafnium is used for
- Nuclear control rods, especially in submarines
- High-k gate dielectrics in processors
- Superalloys for jet engines
- Plasma cutting electrodes
Atomic structure of Hafnium
A neutral hafnium atom has 72 protons and 72 electrons. Its most common isotope carries about 106 neutrons, which is where the mass number 178 comes from. Change the neutron count and you have a different isotope of hafnium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 32, 10, 2. In orbital notation that is [Xe] 6s² 4f¹⁴ 5d². As a d-block element its valence count is variable, which is why it can form compounds in several oxidation states.
3D electron orbitals
See where Hafnium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Hafnium sits in the periodic table
The d-block. Multiple stable oxidation states give them coloured compounds, catalytic ability and the strength that makes them the working metals of industry.
- Directly above: Zirconium — same group, so similar chemistry with a smaller atom.
- Directly below: Rutherfordium — same group, one shell larger.
- One proton lighter: Lutetium.
- One proton heavier: Tantalum.
Discovery and naming
Hafnium was discovered by Dirk Coster and George de Hevesy in 1923. Its name comes from Hafnia, the Latin name for Copenhagen, which is also why its symbol (Hf) does not match its English name.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Hafnium?
The standard atomic weight of Hafnium is 178.49 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Hafnium have?
Hafnium has 72 protons, because the atomic number is the proton count and that is what makes an atom Hafnium at all. A neutral Hafnium atom has the same number of electrons, 72. The neutron count varies by isotope; the most common one has about 106, since 178 − 72 = 106.
What is the electron configuration of Hafnium?
The electron configuration of Hafnium is [Xe] 6s² 4f¹⁴ 5d². Its electrons are arranged 2, 8, 18, 32, 10, 2 across 6 shells.
Is Hafnium a metal?
Yes. Hafnium is classified as a transition metal, on the metallic side of the table.
What group and period is Hafnium in?
Hafnium is in group 4 (the titanium group), period 6, in the d-block. The group is its column and the period is its row.
What is the charge of Hafnium?
Hafnium most commonly forms a 4+ ion. Like most transition metals it has several accessible oxidation states, so the charge depends on the compound.
What is the melting point of Hafnium?
Hafnium melts at 2,233 °C and boils at 4,603 °C. That puts it in the solids at everyday temperatures.
What is Hafnium used for?
Nuclear control rods, especially in submarines, High-k gate dielectrics in processors, Superalloys for jet engines, Plasma cutting electrodes. Hafnium is chemically almost a twin of zirconium but behaves in the exact opposite way toward neutrons — it soaks them up.
Who discovered Hafnium, and where does its name come from?
Hafnium (Hf) was discovered by Dirk Coster and George de Hevesy in 1923. The name comes from Hafnia, the Latin name for Copenhagen.