Final answer:
The number in the carbon location represents the atomic number of carbon, which is 1. This indicates that carbon has 1 proton in its nucleus.
Step-by-step explanation:
The number in the carbon location on the left figure of the carbonate ion (CO₃²⁻) is 1, which refers to the atomic number of carbon. Carbon has an atomic number of 6, indicating that it has 6 protons in its nucleus.