Question

Type a formula for the compound that forms between sodium and each polyatomic ion:

1. Carbonate

2. Phosphate

3. Hydrogen Phosphate

4. Acetate

Answer 1

The sodium ion is Na⁺, so we need to "criss-cross" the charges only.
1. Carbonate is CO3^2-. Just like in hydrogen phosphate, here we cross a 2 onto the sodium. Na2CO3.

2. Phosphate is PO4^3-. You'd criss-cross the three on phosphate down onto the sodium and the 1 on sodium onto the phosphate. Na3PO4
3. Hydrogen phosphate is HPO4^2-. Here, the two would criss-cross down onto the sodium and the 1 onto the hydrogen phosphate. Na2HPO4.
4. Acetate is CH3COO^-. Now, Cross the one on acetate and the 1 on the sodium and get NaCH3COO