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Hafnium (Hf)

Hafnium is a chemical element of the periodic table with chemical symbol Hf and atomic number 72 with an atomic weight of 178.492 u and is classed as transition metal and is part of group 4 (titanium group). Hafnium is solid at room temperature.

Hafnium in the periodic table

Atomic number72
Group4 (Titanium group)
ClassificationTransition Metal
AppearanceSteel gray
Color Gray
Number of protons72 p+
Number of neutrons106 n0
Number of electrons72 e-
From Wikipedia, the free encyclopediaHafnium is a chemical element with symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923, making it the penultimate stable element to be discovered (rhenium was identified two years later).

Physical properties

Phase at STPSolid
Density13.31 g/cm3
Atomic weight178.492 u

Thermal properties

Melting point2506 K
2232.85 °C
4051.13 °F
Boiling point4876 K
4602.85 °C
8317.13 °F
Heat of vaporization661.07 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)1.3
Electron affinity17.18 kJ/mol
Oxidation states−2, 0, +1, +2, +3, +4
(an amphoteric oxide)
Ionization energies
  1. 658.5 kJ/mol
  2. 1440 kJ/mol
  3. 2250 kJ/mol
  4. 3216 kJ/mol

Electron configuration for hafnium

Electron configuration
Shorthand configuration
[Xe] 4f14 5d2 6s2
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d2 6s2
Electron configuration chart
Electrons per shell2, 8, 18, 32, 10, 2
Valence electrons 2
Valency electrons 4
Bohr model
HafniumElectron shell for Hafnium, created by Injosoft ABHf
Figure: Shell diagram of Hafnium (Hf) atom.
Orbital Diagram

The history of Hafnium

PredictionDmitri Mendeleev (1869)
Discovery and first isolationDirk Coster, George de Hevesy (1922)
Discovery of hafnium
In his report on The Periodic Law of the Chemical Elements, in 1869, Dmitri Mendeleev had implicitly predicted the existence of a heavier analog of titanium and zirconium. The X-ray spectroscopy done by Henry Moseley in 1914 showed a direct dependency between spectral line and effective nuclear charge. This led to the nuclear charge, or atomic number of an element, being used to ascertain its place within the periodic table. With this method, Moseley determined the number of lanthanides and showed the gaps in the atomic number sequence at numbers 43, 61, 72, and 75. The discovery of the gaps led to an extensive search for the missing elements. And the reappearance in 1922 of Urbain's claims that element 72 was a rare earth element discovered in 1911, Dirk Coster and Georg von Hevesy were motivated to search for the new element in zirconium ores.Hafnium was discovered by the two in 1923 in Copenhagen, Denmark, validating the original 1869 prediction of Mendeleev. It was ultimately found in zircon in Norway through X-ray spectroscopy analysis. The place where the discovery took place led to the element being named for the Latin name for "Copenhagen", Hafnia, the home town of Niels Bohr.


List of unique identifiers for Hafnium in various chemical registry databases
CAS Number7440-58-6
ChemSpider ID22422
EC number231-166-4
PubChem CID Number23986