Check out this answer from Consensus:
The charge of a carbon ion varies significantly depending on its chemical environment and structural form. Empirical relations can predict the core electron binding energy based on the charge, and specific carbon clusters can exhibit stable doubly negative charges. Additionally, the charge distribution in carbon materials is often inhomogeneous, influenced by the surrounding environment and structural configuration.
The charge of a carbon ion is a fundamental property that varies depending on the specific form and environment of the carbon atom. This property is crucial in understanding the behavior of carbon in different chemical and physical contexts.
Key Insights
- Empirical Relation for Core Electron Binding Energy:
- The core electron binding energy (Eb) of carbon atoms can be empirically related to the charge on the carbon atoms (qc) using the formula: Eb(C1s) = 6.42qc + 4.52q2c + 285.8 eV. This relation holds for various carbon-containing species, including substituted aromatic compounds and the cyanide ion1.
- Doubly Charged Negative Carbon Cluster Ions:
- Carbon cluster ions with a double negative charge (C_n^2−) have been produced by sputtering graphite. These ions have lifetimes of at least 10 microseconds and exhibit an alternating intensity pattern based on the number of carbon atoms (n) in the cluster2.
- Charge Inhomogeneity in Carbon Materials:
- The charge distribution in carbon materials is often inhomogeneous. For example, in certain carbon structures like C10 rings, C24, and C60 fullerenes, the charge is zero, while in other structures like pentagon C10 rings, C30, and C70 fullerenes, the charge is not zero. Additionally, carbon atoms at the ends of atomistic chains, nanotubes, or on the edges of graphenes have larger positive or negative charges, whereas the central parts have almost zero charge. In diamond and graphite, the charge is zero, but it is not zero in high-pressure solid phases like hexagonite or on some carbon surfaces3.