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.

plants need sunlight, water, and carbon dioxide to make food. plants use the raw materials of water, nutrients they absorb from soil, and carbon dioxide to make sugars the plant can use. energy from the sun and chlorophyll are also needed.