How to find the valency of a polyatomic ion?

The valencies of the constituent atoms are combined by the poly atomic ion, carbonate, has a formula of CO3 the valence state it is in of oxygen ions is -2 the periodic table group it’s in Group 16 the two to the left of Group 18, the noble gases: 16–18 = -2) and their are 3 oxygen atoms in the poly atomic ion, so the oxygen atoms contribute -6 to the valency of the poly atomic ion. The one carbon atom has a valency of 4+. The overall charge on the carbonate ion is -6 +4 = -2. So carbonate has a charge of -2.

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.

a electronegativity decreases beacuse the size of nucleus is bigger.