Skip to the content
Browse the library

Ruthenium (Ru)

Ruthenium is the 44th element, a transition metal in the d-block. Its standard atomic weight is 101.07.

Period 5Group 8d-blockTransition metal
44Ru

Ruthenium

101.07

What the table records

Atomic number
44
Standard atomic weight
101.07
Group
8
Period
5
Block
d-block
Category
Transition metal
Electron configuration
[Kr] 4d7 5s1
Valence electrons
8
Typical valence
Variable — no single default
Van der Waals radius
2.05 Å
Covalent radius
1.46 Å

The configuration above is the documented ground state (departs from the aufbau order).

How to read these numbers

The standard atomic weight is an average over the isotopes as they occur naturally, which is why it is rarely a whole number. It is the figure a molar mass calculation uses. Work in mass spectrometry wants the monoisotopic mass of a single isotope instead, which is a different number.

The two radii are not the same measurement. The covalent radius is half the distance between two bonded atoms of the element; the van der Waals radius is how close a non-bonded atom gets before repulsion takes over, and is always the larger. Space-filling models are drawn with the second, ball-and-stick models with the first — which is why the same molecule looks so different in the two.