This is true, this isn't a question, it's a fact.
The equation that shows the formation of chromium (ii) ion from neutral chromium atom is as follow
Cr ---> cr^2+ + 2e-
Cr^2+ is the chromium ion with oxidation state of two which is one of the common ion of chromium. Other common ion of chromium include chromium of oxidation state 6 and 3
Tarnish is Ag2S-silver sulfide and the oxidation state of silver is +1
