What does CoCN 3 mean?

Answer 1

Co(CN)3 is Cobalt(III)cyanide or cobalt(III)nitrile.

NB You have written this formula rather poorly.

As given the '3' only represents three nitrogens.

However, when written with brackets as (CN)3 it means that there are three nitrile(cyano) anions present in the molecule.

Co ; 1 x Cobalt

C ; 3 x Carbon

N ; 3 x Nitrogen .

Answer 2

Cobaltic Cyanide or Cobalt (III) Cyanide