044Transition metal · Group 8 · Period 5

Ruthenium

Ruthenium (Ru) is element 44, a transition metal in the d-block — group 8, period 5. It is a solid at room temperature with 5 electron shells (2, 8, 18, 15, 1) and an atomic mass of 101.072 u.

Atomic mass: 101.1 u
Phase · STP: solid
Melting: 2607 K · 2334 °C
Boiling: 4423 K · 4150 °C
Electronegativity: 2.2
Density: 12.45 g/cm³

Photograph — Hi-Res Images ofChemical Elements, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons, source: https://images-of-elements.com/ruthenium.php

Identity

Atomic number: 44
Standard atomic weight: 101.1 u
Category: Transition metal
Group: 8
Period: 5
Block: d-block
Oxidation states: +3

Physical properties

Melting point: 2607 K · 2334 °C
Boiling point: 4423 K · 4150 °C
Density: 12.45 g/cm³
Molar heat capacity: 24.06 J/(mol·K)
Atomic radius: 207 pm
Electron affinity: 100.96 kJ/mol

Atomic structure

44protons

57neutrons

44electrons

1valence e⁻

Noble-gas notation: [Kr] 4d7 5s1
Full configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d7
Electrons per shell: 2, 8, 18, 15, 1

Periodic trends

Where Ruthenium ranks across all 118 elements.

Electronegativity2.2

Ionization energy710.2 kJ/mol

Electron affinity100.96 kJ/mol

Density12.45 g/cm³

Atomic radius207 pm

Ionization energies

Energy to remove each successive electron (kJ/mol).

710.2

1.6k

2.7k

Successive ionization energies (kJ/mol, log scale).

Discovery

Discovered: 1827
Discovered by: Karl Ernst Claus
Named by: —
Appearance: silvery white metallic