Ruthenium (Ru)
Ruthenium is element 44, a transition metal in period 5, group 8 of the periodic table. At room temperature it is a solid.
Electron configuration [Kr] 4d7 5s1
Electrons per shell 2, 8, 18, 15, 1
Ruthenium data
| Atomic number | 44 |
|---|---|
| Symbol | Ru |
| Atomic mass | 101.07 u |
| Category | Transition metal |
| Group | 8 |
| Period | 5 |
| Block | d |
| State at 25 °C | solid |
| Melting point | 2607 K (2333.9 °C) |
| Boiling point | 4423 K (4149.9 °C) |
| Density | 12.37 g/cm³ |
| Electronegativity (Pauling) | 2.2 |
| Atomic radius | 126 pm |
| 1st ionization energy | 710 kJ/mol |
| Electron affinity | -101 kJ/mol |
| Oxidation states | -2, +1, +2, +3, +4, +5, +6, +7, +8 |
| Common ion charge | 3+ |
| Discovered | 1827 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through ruthenium’s configuration and its ions →
Where ruthenium sits
Ruthenium belongs to the transition metals. Its Pauling electronegativity of 2.2 is mid-range; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Ruthenium FAQ
What is the electron configuration of ruthenium?
Ruthenium (Z = 44) has the configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d7 5s1. In noble-gas shorthand that is [Kr] 4d7 5s1. This is an exception to the simple Aufbau prediction (1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d6 5s2); a half-filled or filled subshell lowers the energy.
How many valence electrons does ruthenium have?
8 (1 outer s + 7 d electrons; 1 in the outermost shell).
What is the atomic mass of ruthenium?
The standard atomic weight of ruthenium is 101.07 u, so one mole weighs 101.07 g.
Is ruthenium a metal?
Yes. Ruthenium is a transition metal.
What is the charge of a ruthenium ion?
Ruthenium most commonly forms Ru3+.