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Hf

Hafnium

Hafnium (Hf) is a transition metal with atomic number 72 and an atomic mass of 178.49. Its electron configuration is [Xe] 4f14 5d2 6s2.

Hafnium key data

Symbol Hf
Atomic number 72
Atomic mass (standard atomic weight) 178.49
Molar mass 178.49 g/mol
Protons 72
Neutrons (most abundant isotope, hafnium-180) 108
Electrons (neutral atom) 72
Category Transition metal
Period 6
Group 4
Block d-block
Noble gas notation [Xe] 4f14 5d2 6s2
Full electron configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d2 6s2
Electrons per shell 2, 8, 18, 32, 10, 2

Atomic mass: IUPAC CIAAW abridged standard atomic weights, 2024. Most abundant isotope: NIST Atomic Weights and Isotopic Compositions.

The values are facts and free to use; this page’s selection and presentation are © 2026 ScienceQuest.

Measured properties of hafnium

From PubChem, the US National Institutes of Health. Public domain. PubChem’s periodic table gives no value for the rows not shown.

Melting point 2506 K (2232.9 °C), 10th of 103 by melting point
Boiling point 4876 K (4602.9 °C), 8th of 93 by boiling point
Density 13.3 g/cm³, 16th of 96 by density
State at room temperature Solid
Electronegativity 1.3 (Pauling), joint 61st of 95 by electronegativity
Van der Waals radius 212 pm, 43rd of 99 by atomic radius
First ionisation energy 6.825 eV (658.5 kJ/mol), 53rd of 102 by first ionisation energy
Common oxidation states +4
Discovered 1923

Each rank counts down from the highest value, among the elements PubChem’s table gives one for, and links to that property ranked across the whole table. All of them are collected under periodic trends.

Hafnium electron configuration

The full electron configuration of hafnium is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d2 6s2. With the noble-gas core collapsed it is [Xe] 4f14 5d2 6s2, and the outermost subshell is 6s2.

Bohr model of hafnium (Hf): a nucleus and six shells holding 2, 8, 18, 32, 10 and 2 electrons from the inside out.
Bohr model of hafnium (Hf). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.
Orbital box diagram of hafnium (Hf), [Xe] 4f14 5d2 6s2, with the xenon core drawn as one bar: one box per orbital, filled by Hund’s rule, showing two unpaired electrons, in 5d.
Orbital diagram of hafnium (Hf). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.

Mass of one hafnium atom

A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.

Mass of one atom

  1. one atom = 178.49 / (6.02214076 × 10²³)
  2. = 2.9639 × 10⁻²² g

Atoms in one gram

  1. atoms per gram = 6.02214076 × 10²³ / 178.49
  2. = 3.3739 × 10²¹ atoms

Hafnium on the periodic table

Hafnium is in period 6, group 4, in the d-block.

The other elements of group 4 are titanium, zirconium and rutherfordium.

The rest of period 6

Work with hafnium