---
title: "Ruthenium (Ru) — element 44"
description: "Ruthenium is element 44, symbol Ru, atomic weight 101.07. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/ruthenium/
site: "At One Place"
---

# Ruthenium (Ru)

**Ruthenium — element 44: Ru**

101.07 u · Transition metal · period 5, group 8

Grubbs catalysts, ruthenium complexes that let chemists swap the ends of carbon-carbon double bonds under mild conditions, won the 2005 Nobel Prize in Chemistry and are now routine in pharmaceutical synthesis. Ruthenium is one of the rarest elements in the crust at about one part per billion, and nearly all of it comes as a by-product of platinum and nickel mining in South Africa and Russia. In 2017 a plume of ruthenium-106 drifted across Europe at levels far above background; it was traced by its isotope ratios to a reprocessing accident in the southern Urals that Russia has never acknowledged.

## Properties

- **Atomic number:** 44
- **Symbol:** Ru
- **Standard atomic weight:** 101.07 u
- **Category:** Transition metal
- **Group:** 8
- **Period:** 5
- **Block:** d-block
- **Electron configuration:** [Kr] 5s¹ 4d⁷
- **Electrons per shell:** 2, 8, 18, 15, 1
- **Melting point:** 2,607 K — 2333.8 °C — 4232.9 °F
- **Boiling point:** 4,423 K — 4149.9 °C — 7501.7 °F
- **Density:** 12.1 g/cm³
- **Electronegativity:** 2.2 (Pauling)
- **Oxidation states:** +3, +4, +8
- **Discovered:** 1844 by Karl Ernst Claus

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹ 4d⁷
- **Noble gas shorthand:** [Kr] 5s¹ 4d⁷
- **Shells:** K: 2 · L: 8 · M: 18 · N: 15 · O: 1

## What it is used for

- Hardening platinum and palladium in electrical contacts and jewellery
- Thick-film resistors in almost all surface-mount electronics
- Ruthenium catalysts for ammonia synthesis and olefin metathesis
- Fountain pen nib tips, alloyed with iridium and osmium
- Dye-sensitised solar cell sensitisers

> Anomalous electron configuration: [Kr] 5s¹ 4d⁷ rather than the predicted 5s² 4d⁶.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 42 | Molybdenum | Mo | 95.95 |
| 43 | Technetium | Tc | [97] |
| 44 | Ruthenium ← | Ru | 101.07 |
| 45 | Rhodium | Rh | 102.91 |
| 46 | Palladium | Pd | 106.42 |

## Group 8

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Ruthenium sits in group 8 with iron, osmium, hassium.

## Common questions

### What is the atomic number of ruthenium?

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

### What is the symbol for ruthenium?

Ru.

### What is the electron configuration of ruthenium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹ 4d⁷, or [Kr] 5s¹ 4d⁷ in noble-gas shorthand.

### What is the melting point of ruthenium?

2,607 K — 2333.8 °C — 4232.9 °F

## Related pages

- [Molybdenum (Mo)](https://atoneplace.net/element/molybdenum/)
- [Technetium (Tc)](https://atoneplace.net/element/technetium/)
- [Rhodium (Rh)](https://atoneplace.net/element/rhodium/)
- [Palladium (Pd)](https://atoneplace.net/element/palladium/)
- [Iron (Fe)](https://atoneplace.net/element/iron/)
- [Osmium (Os)](https://atoneplace.net/element/osmium/)
- [Hassium (Hs)](https://atoneplace.net/element/hassium/)

## Sources

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