Answer:
In addition to carbonyl and organometallic compounds in the low oxidation states −2, 0, and +1, ruthenium forms compounds in every oxidation state from +2 to +8. Very volatile ruthenium tetroxide, RuO4, used in separating ruthenium from other heavy metals, contains the element in the +8 oxidation state.
Valence: 1, 2, 3, 4, 5, 6, 7, 8
Melting point: 2,250° C (4,082° F)
and the most stable oxidation state of ruthenium is +8