Zirconium (Zr)
Element 40 · Transition metal · atomic mass 91.222 u · group 4, period 5
Electron shells: 2, 8, 18, 10, 2
Zirconium barely absorbs neutrons and resists corrosion superbly, a combination that makes it the standard cladding for nuclear fuel rods. Its oxide is a convincing diamond substitute.
Nearly every nuclear fuel rod on Earth is wrapped in zirconium alloy.
- Atomic number
- 40
- Atomic mass
- 91.222 u
- Electron configuration
- [Kr] 5s² 4d²
- Group · period · block
- 4 · 5 · d
- Oxidation states
- +4
- Electronegativity
- 1.33 (Pauling)
- Melting point
- 1,855 °C
- Boiling point
- 4,409 °C
- Density
- 6.52 g/cm³
- State at 20 °C
- Solid
- Appearance
- Greyish-white, lustrous metal
- Discovered
- Martin Heinrich Klaproth, 1789
40 protons, and 40 electrons when neutral
IUPAC standard atomic weight
Titanium group
What Zirconium is used for
- Nuclear fuel rod cladding
- Cubic zirconia gemstones
- Dental crowns and ceramics
- Chemical plant piping
Atomic structure of Zirconium
A neutral zirconium atom has 40 protons and 40 electrons. Its most common isotope carries about 51 neutrons, which is where the mass number 91 comes from. Change the neutron count and you have a different isotope of zirconium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 10, 2. In orbital notation that is [Kr] 5s² 4d². As a d-block element its valence count is variable, which is why it can form compounds in several oxidation states.
3D electron orbitals
See where Zirconium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Zirconium sits in the periodic table
The d-block. Multiple stable oxidation states give them coloured compounds, catalytic ability and the strength that makes them the working metals of industry.
Discovery and naming
Zirconium was discovered by Martin Heinrich Klaproth in 1789. Its name comes from Persian zargun, "gold-like", which is also why its symbol (Zr) does not match its English name.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Zirconium?
The standard atomic weight of Zirconium is 91.222 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Zirconium have?
Zirconium has 40 protons, because the atomic number is the proton count and that is what makes an atom Zirconium at all. A neutral Zirconium atom has the same number of electrons, 40. The neutron count varies by isotope; the most common one has about 51, since 91 − 40 = 51.
What is the electron configuration of Zirconium?
The electron configuration of Zirconium is [Kr] 5s² 4d². Its electrons are arranged 2, 8, 18, 10, 2 across 5 shells.
Is Zirconium a metal?
Yes. Zirconium is classified as a transition metal, on the metallic side of the table.
What group and period is Zirconium in?
Zirconium is in group 4 (the titanium group), period 5, in the d-block. The group is its column and the period is its row.
What is the charge of Zirconium?
Zirconium most commonly forms a 4+ ion. Like most transition metals it has several accessible oxidation states, so the charge depends on the compound.
What is the melting point of Zirconium?
Zirconium melts at 1,855 °C and boils at 4,409 °C. That puts it in the solids at everyday temperatures.
What is Zirconium used for?
Nuclear fuel rod cladding, Cubic zirconia gemstones, Dental crowns and ceramics, Chemical plant piping. Zirconium barely absorbs neutrons and resists corrosion superbly, a combination that makes it the standard cladding for nuclear fuel rods.
Who discovered Zirconium, and where does its name come from?
Zirconium (Zr) was discovered by Martin Heinrich Klaproth in 1789. The name comes from Persian zargun, "gold-like".