---
title: "Hafnium (Hf) — element 72"
description: "Hafnium is element 72, symbol Hf, atomic weight 178.49. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/hafnium/
site: "At One Place"
---

# Hafnium (Hf)

**Hafnium — element 72: Hf**

178.49 u · Transition metal · period 6, group 4

Hafnium and zirconium sit directly above and below each other and are so alike that separating them is one of the harder industrial separations there is — yet the separation is essential, because zirconium is transparent to neutrons and hafnium absorbs them greedily. Reactor cladding must be hafnium-free zirconium; reactor control rods are the hafnium that was taken out. Since about 2007 every leading-edge processor has used a hafnium oxide gate dielectric, because silicon dioxide had been thinned to a few atoms and was leaking; hafnium was what let Moore's law continue past 45 nm.

## Properties

- **Atomic number:** 72
- **Symbol:** Hf
- **Standard atomic weight:** 178.49 u
- **Category:** Transition metal
- **Group:** 4
- **Period:** 6
- **Block:** d-block
- **Electron configuration:** [Xe] 6s² 4f¹⁴ 5d²
- **Electrons per shell:** 2, 8, 18, 32, 10, 2
- **Melting point:** 2,506 K — 2232.8 °C — 4051.1 °F
- **Boiling point:** 4,876 K — 4602.9 °C — 8317.1 °F
- **Density:** 13.3 g/cm³
- **Electronegativity:** 1.3 (Pauling)
- **Oxidation states:** +4
- **Discovered:** 1923 by Dirk Coster and George de Hevesy

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d²
- **Noble gas shorthand:** [Xe] 6s² 4f¹⁴ 5d²
- **Shells:** K: 2 · L: 8 · M: 18 · N: 32 · O: 10 · P: 2

## What it is used for

- Control rods in naval reactors, where neutron absorption matters most
- Hafnium oxide as the high-k gate dielectric in modern processors
- Nickel superalloys for turbine blades
- Plasma cutting torch electrodes

> CIAAW gives 178.486; 178.49 is the abridged value. Named after Hafnia, the Latin name for Copenhagen, where it was found in Bohr's institute — and its discovery confirmed Bohr's prediction that element 72 would be a transition metal rather than a rare earth.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 70 | Ytterbium | Yb | 173.05 |
| 71 | Lutetium | Lu | 174.97 |
| 72 | Hafnium ← | Hf | 178.49 |
| 73 | Tantalum | Ta | 180.95 |
| 74 | Tungsten | W | 183.84 |

## Group 4

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Hafnium sits in group 4 with titanium, zirconium, rutherfordium.

## Common questions

### What is the atomic number of hafnium?

72. That is the number of protons in its nucleus, which is what defines the element.

### What is the symbol for hafnium?

Hf.

### What is the electron configuration of hafnium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d², or [Xe] 6s² 4f¹⁴ 5d² in noble-gas shorthand.

### What is the melting point of hafnium?

2,506 K — 2232.8 °C — 4051.1 °F

## Related pages

- [Ytterbium (Yb)](https://atoneplace.net/element/ytterbium/)
- [Lutetium (Lu)](https://atoneplace.net/element/lutetium/)
- [Tantalum (Ta)](https://atoneplace.net/element/tantalum/)
- [Tungsten (W)](https://atoneplace.net/element/tungsten/)
- [Titanium (Ti)](https://atoneplace.net/element/titanium/)
- [Zirconium (Zr)](https://atoneplace.net/element/zirconium/)
- [Rutherfordium (Rf)](https://atoneplace.net/element/rutherfordium/)

## Sources

- Official vendor product documentation — At One Place (/about/)