---
title: "Zirconium (Zr): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/zirconium.html
description: "Zirconium (Zr), element 40: atomic mass 91.224, electron configuration [Kr] 4d² 5s², group 4, period 5, d-block transition metal. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
40Zr91.224

# Zirconium (Zr) – element 40

Zirconium is a chemical element with the symbol **Zr** and atomic number **40**. It is a transition metal in group 4, period 5 of the periodic table (d-block), and is a solid at room temperature.

Zirconium (Zr) has atomic number 40, atomic mass 91.224 u and electron configuration [Kr] 4d2 5s2.

[Download periodic table PDF](https://www.moldraw.com/printables/periodic-table.pdf)[Open interactive periodic table](https://www.moldraw.com/tools/free-chem-tools/interactive-periodic-table.html)

## Zirconium facts

| Symbol | Zr |
| --- | --- |
| Atomic number | 40 |
| Atomic mass | 91.224 u (g/mol) |
| Category | transition metal |
| Group | group 4 |
| Period | 5 |
| Block | d-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d2 |
| Noble-gas notation | [Kr] 4d2 5s2 |
| Electrons per shell | 2, 8, 18, 10, 2 |

## Bohr model and shells

Zirconium has 40 electrons in 5 shells: 2, 8, 18, 10, 2. Full configuration and noble-gas notation are in the table; work out any element or ion with the [electron configuration calculator](https://www.moldraw.com/tools/free-chem-tools/electron-configuration-calculator.html).

## Physical and atomic properties

| Melting point | 2128 K (1854.8 °C) |
| --- | --- |
| Boiling point | 4650 K (4376.9 °C) |
| Density | 6.52 g/cm³ |
| Electronegativity (Pauling) | 1.33 |
| Electron affinity | 41.806 kJ/mol |
| Ionization energies | 640.1, 1270, 2218 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 25.36 J/(mol·K) |
| Discovered by | Martin Heinrich Klaproth |

Use the atomic mass in the [molar mass calculator](https://www.moldraw.com/tools/free-chem-tools/molar-mass-calculator.html) for any formula containing Zr.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of zirconium?

The atomic mass of zirconium is 91.224 u, so one mole of zirconium atoms weighs 91.224 g.

### What is the electron configuration of zirconium?

Zirconium has 40 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d², or [Kr] 4d² 5s² in noble-gas notation. Electrons per shell: 2, 8, 18, 10, 2.

### Is zirconium a metal?

Yes. Zirconium is a transition metal.

### Where is zirconium on the periodic table?

Zirconium is in group 4, period 5, in the d-block.

Data: [Periodic-Table-JSON](https://github.com/Bowserinator/Periodic-Table-JSON) (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.