Transition metalElement 72 · d-block

Hafnium (Hf)

Hafnium (Hf) is a transition metal with atomic number 72 and a standard atomic weight of 178.49. At room temperature it is a solid that melts at 2,233 °C and boils at 4,600 °C.

72HfHafnium178.49

Atomic number

protons

Atomic weight

178.49

CIAAW 2024

Melting point

2,233 °C

2,506.15 K

Boiling point

4,600 °C

4,873.15 K

Density

13.3 g/cm³

near room temperature

Electronegativity

1.3

Pauling scale

State at 25 °C

Solid

Discovered

1923

Denmark

Hafnium at a glance

Identity

Symbol	Hf
Atomic number (Z)	72
Atomic weight	178.49 ± 0.01 (CIAAW 2024)
Category	Transition metal
Group	4
Period	6
Block	d-block
CAS number	7440-58-6

Atomic properties

Electron configuration	[Xe] 4f¹⁴ 5d² 6s² Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d² 6s²
Electrons per shell	2, 8, 18, 32, 10, 2
Oxidation states	+4 Less common: -2, 0, +1, +2, +3
Electronegativity (Pauling)	1.3
First ionisation energy	6.825 eV (658.5 kJ/mol) 2nd: 14.61 eV · 3rd: 22.55 eV
Electron affinity	0.014 eV
Atomic radius (empirical)	155 pm
Covalent radius	152 pm
Van der Waals radius	223 pm

Physical properties

State at 25 °C	Solid
Melting point	2,233 °C · 4,051.4 °F · 2,506.15 K
Boiling point	4,600 °C · 8,312 °F · 4,873.15 K
Density	13.3 g/cm³
Specific heat capacity	0.144 J/(g·K)
Thermal conductivity	23 W/(m·K)
Crystal structure	Hexagonal

Isotopes & abundance

Natural occurrence	Primordial
Radioactive	No
Natural isotopes (abundance)	¹⁸⁰Hf 35.08%, ¹⁷⁸Hf 27.28%, ¹⁷⁷Hf 18.6%, ¹⁷⁹Hf 13.62%, ¹⁷⁶Hf 5.26%, ¹⁷⁴Hf 0.16% (radioactive)
Stable isotopes	5
Known isotopes	38
Abundance in Earth's crust	3 mg/kg
Abundance in seawater	0.000007 mg/L

Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.

Hafnium electron configuration

Hafnium has 72 electrons. Written in short form, its ground-state configuration is [Xe] 4f¹⁴ 5d² 6s² — the electrons of the noble gas xenon, plus 4f¹⁴ 5d² 6s².Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d² 6s².

4f↑↓↑↓↑↓↑↓↑↓↑↓↑↓

5d↑↑

6s↑↓

Discovery and name

Discovered

1923 — Dirk Coster and George de Hevesy · Denmark.

Name

Latin Hafnia, Copenhagen.

Known for

Absorbs neutrons well, so used in nuclear control rods; hafnium oxide is the insulating layer in modern microchip transistors.

Isotopes of hafnium

Naturally occurring hafnium is a mix of 6 isotopes. Each has 72 protons; they differ in the number of neutrons:

Isotope	Protons	Neutrons	Natural abundance	Stability
¹⁸⁰Hf	72	108	35.08%	stable
¹⁷⁸Hf	72	106	27.28%	stable
¹⁷⁷Hf	72	105	18.6%	stable
¹⁷⁹Hf	72	107	13.62%	stable
¹⁷⁶Hf	72	104	5.26%	stable
¹⁷⁴Hf	72	102	0.16%	radioactive · half-life 2 × 10¹⁵ years

38 isotopes of hafnium are known in our data set (half-lives as published in nuclear data tables).

Hafnium compared with group 4

The other elements in group 4, from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Titanium	22	47.867	1,670 °C	3,287 °C	4.506 g/cm³	1.54
Zirconium	40	91.222	1,854 °C	4,406 °C	6.52 g/cm³	1.33
Hafnium	72	178.49	2,233 °C	4,600 °C	13.3 g/cm³	1.3
Rutherfordium	104	[267]	—	—	23.3 g/cm³ (pred.)	—

Frequently asked questions

6 answers

What is the atomic mass of hafnium?

The standard atomic weight of hafnium is 178.49 ± 0.01 (CIAAW 2024), so one mole weighs about 178.49 grams.

How many protons, neutrons and electrons does hafnium have?

A neutral hafnium atom has 72 protons and 72 electrons. Its most common isotope, hafnium-180, has 108 neutrons.

What is the electron configuration of hafnium?

[Xe] 4f¹⁴ 5d² 6s² (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d² 6s²).

What are the melting and boiling points of hafnium?

Hafnium melts at 2,233 °C (4,051.4 °F) and boils at 4,600 °C (8,312 °F).

Is hafnium a metal?

Hafnium is a metal. It is in group 4, period 6, and is a solid at room temperature.

Who discovered hafnium?

1923 — Dirk Coster and George de Hevesy (Denmark).