Hafnium
Hafnium is a transition metal chemically similar to zirconium but much more effective at absorbing neutrons.
Hafnium is zirconium's close relative with a very different response to neutrons.
Explore Hafnium's atom- Atomic number
- 72
- Standard atomic weight
- 178.486(6)
- Family
- Transition metal
- Period
- 6
- Group
- 4
- Standard state
- Solid
In everyday life
Hafnium is used in reactor control rods and advanced electronic materials.
Something to remember
Hafnium absorbs neutrons readily, whereas zirconium absorbs relatively few.
Meet its electrons
[Xe] 6s2 4f14 5d2
Published neutral-atom ground-state configuration; excited atoms and ions can differ.
Electrons per shell: 2 · 8 · 18 · 32 · 10 · 2.
The playground shows an illustrative shell model. Real electrons are described by quantum orbitals, rather than tiny planets traveling along fixed paths.
A connection to explore
Hafnium and zirconium have similar chemistry but very different neutron absorption.
Meet Zirconium (Zr)Properties and conditions
- Standard atomic weight
- 178.486(6)CIAAW 2024 standard atomic weight (dimensionless). Parentheses give uncertainty in the last quoted digits. Source flags: g.CIAAW standard atomic weights ↗ · Retrieved 2026-10-15
- Standard state
- SolidPubChem classification, including explicit predictions where stated. Reference temperature and pressure are not supplied in the table.PubChem periodic table ↗ · Retrieved 2026-10-15
- First ionisation energy
- 6.825 eVEnergy to remove the first electron from an isolated neutral gas-phase atom. Uncertainty is not supplied.PubChem periodic table ↗ · Retrieved 2026-10-15
- Electronegativity
- 1.3 Pauling scaleA dimensionless relative measure; values depend on the chosen scale. Uncertainty is not supplied.PubChem periodic table ↗ · Retrieved 2026-10-15
- Melting point
- 2506 KPubChem reported value. Pressure, allotrope and measurement uncertainty are not specified in the table; consult the cited source.PubChem periodic table ↗ · Retrieved 2026-10-15
- Boiling point
- 4876 KPubChem reported value. Pressure and measurement uncertainty are not specified in the table; consult the cited source.PubChem periodic table ↗ · Retrieved 2026-10-15
- Density
- 13.3 g/cm³PubChem reported value. Temperature, pressure, allotrope and measurement uncertainty are not specified in the table; gas densities are especially condition-dependent.PubChem periodic table ↗ · Retrieved 2026-10-15
- Oxidation states
- +4Selected PubChem oxidation states; formal electron bookkeeping, not a list of stable free-ion charges or every possible compound.PubChem periodic table ↗ · Retrieved 2026-10-15
- Discovery
- 1923PubChem discovery attribution. Ancient knowledge and competing priority claims cannot always be represented by a single year.PubChem periodic table ↗ · Retrieved 2026-10-15
- Atomic radius
- 212 pmPubChem tabulated radius. Radius definitions depend on bonding and convention; measurement definition and uncertainty are not supplied in this table.PubChem periodic table ↗ · Retrieved 2026-10-15
- Electron affinity
- Not reportedPubChem reported gas-phase electron affinity. Sign conventions and electronic states matter; uncertainty is not supplied in this table.PubChem periodic table ↗ · Retrieved 2026-10-15
Isotopes, abundance and decay
Isotopes share a proton count but have different neutron counts. This selection includes naturally tabulated compositions and a reference isotope for other elements. It is not a list of every known isotope.
Explore 6 isotopes of Hf
| Isotope | Relative atomic mass | Natural fraction | Half-life | Decay |
|---|---|---|---|---|
| Hf-174 | 173.9400461(28) | 0.0016(1) | 2.0 Py (uncertainty 0.4) | ;α=100;2β+ ? |
| Hf-176 | 175.9414076(22) | 0.0526(7) | No decay observed | No decay tabulated |
| Hf-177 | 176.9432277(20) | 0.1860(9) | No decay observed | No decay tabulated |
| Hf-178 | 177.9437058(20) | 0.2728(7) | No decay observed | No decay tabulated |
| Hf-179 | 178.9458232(20) | 0.1362(2) | No decay observed | No decay tabulated |
| Hf-180 | 179.9465570(20) | 0.3508(16) | No decay observed | No decay tabulated |
Fractions use NIST’s terrestrial isotopic compositions, which can vary by sample. Parentheses denote uncertainty in the last digits. Half-lives and decay branches use NUBASE2020; # marks estimates, >/< mark limits. “No decay observed” follows that evaluation and does not prove permanent stability. Decay branch intensities are percentages; SF means spontaneous fission, EC electron capture, IT an isomeric transition.
Follow the science
Use these original references to explore the data and context. Atomic weights can vary with isotope composition; values for elements without stable isotopes may describe a representative isotope rather than a standard atomic weight.