---
title: "Ruthenium (Ru): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/ruthenium.html
description: "Ruthenium (Ru), element 44: atomic mass 101.07, electron configuration [Kr] 4d⁷ 5s¹, group 8, period 5, d-block transition metal. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
44Ru101.07

# Ruthenium (Ru) – element 44

Ruthenium is a chemical element with the symbol **Ru** and atomic number **44**. It is a transition metal in group 8, period 5 of the periodic table (d-block), and is a solid at room temperature.

Ruthenium (Ru) has atomic number 44, atomic mass 101.07 u and electron configuration [Kr] 4d7 5s1.

[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)

## Ruthenium facts

| Symbol | Ru |
| --- | --- |
| Atomic number | 44 |
| Atomic mass | 101.07 u (g/mol) |
| Category | transition metal |
| Group | group 8 |
| Period | 5 |
| Block | d-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d7 |
| Noble-gas notation | [Kr] 4d7 5s1 |
| Electrons per shell | 2, 8, 18, 15, 1 |

## Bohr model and shells

Ruthenium has 44 electrons in 5 shells: 2, 8, 18, 15, 1. 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 | 2607 K (2333.8 °C) |
| --- | --- |
| Boiling point | 4423 K (4149.9 °C) |
| Density | 12.45 g/cm³ |
| Electronegativity (Pauling) | 2.2 |
| Electron affinity | 100.96 kJ/mol |
| Ionization energies | 710.2, 1620, 2747 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 24.06 J/(mol·K) |
| Discovered by | Karl Ernst Claus |

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 Ru.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of ruthenium?

The atomic mass of ruthenium is 101.07 u, so one mole of ruthenium atoms weighs 101.07 g.

### What is the electron configuration of ruthenium?

Ruthenium has 44 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹ 4d⁷, or [Kr] 4d⁷ 5s¹ in noble-gas notation. Electrons per shell: 2, 8, 18, 15, 1.

### Is ruthenium a metal?

Yes. Ruthenium is a transition metal.

### Where is ruthenium on the periodic table?

Ruthenium is in group 8, 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.