Ruthenium (Ru): electron configuration, atomic mass and facts
Ruthenium (Ru) is element 44 of the periodic table, a transition metal in period 5, group 8. Its electron configuration is [Kr] 4d7 5s1, with electrons arranged in shells 2, 8, 18, 15, 1, and its standard atomic weight is 101.07 u.
▶ Watch Ruthenium’s electrons orbit in the interactive periodic tableRuthenium at a glance
| Symbol | Ru |
|---|---|
| Atomic number | 44 |
| Atomic mass | 101.07 u |
| Category | Transition metal |
| Group | 8 |
| Period | 5 |
| Block | d-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d7 5s1 |
| Noble-gas shorthand | [Kr] 4d7 5s1 |
| Electrons per shell | 2, 8, 18, 15, 1 |
| Electronegativity (Pauling) | 2.2 |
| State at 20 °C | solid |
Where is Ruthenium on the periodic table?
Ruthenium is in period 5, group 8, in the d-block. The period number matches its 5 electron shells, and the block names the subshell its last electrons fill. In the same group, Iron sits directly above it and Osmium sits directly below it. Elements in the same column of the d-block often have similar chemistry.
How to work out the electron configuration of Ruthenium
Put 44 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p⁶ (10), 3s² (12), 3p⁶ (18), 4s² (20), 3d¹⁰ (30), 4p⁶ (36), 5s² (38), 4d⁶ (44). Ruthenium is one of the exceptions to this filling order: experiments show its ground state is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹ 4d⁷ rather than 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d⁶, because the neighbouring subshells are so close in energy. In shorthand, [Kr] stands for the 36 electrons of krypton, giving [Kr] 4d⁷ 5s¹.
How electronegative is Ruthenium?
Ruthenium has a Pauling electronegativity of 2.2, ranking 17 of the 100 elements with a known value (fluorine is highest at 3.98). That is in the middle of the range.
Frequently asked questions
What is the electron configuration of Ruthenium?
The electron configuration of Ruthenium (Ru) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d7 5s1. In noble-gas shorthand it is written [Kr] 4d7 5s1.
How many electrons does Ruthenium have in each shell?
Ruthenium has 44 electrons arranged in shells as 2, 8, 18, 15, 1.
What is the atomic mass of Ruthenium?
The standard atomic weight of Ruthenium is 101.07 u, so one mole of Ruthenium atoms has a mass of about 101.07 g.
Is Ruthenium a metal?
Yes. Ruthenium is a transition metal.
Explore nearby elements
More transition metals: Niobium, Molybdenum, Technetium, Rhodium, Palladium, Silver. See all elements on the periodic table.