Carbanion
A carbon species carrying a negative charge on the carbon atom is known as a carbanion.

Explanation:
When a carbon atom gains an electron, it becomes negatively charged and forms a carbanion. This negative charge is localized on the carbon atom and is represented by a superscript minus sign (-) next to the carbon atom.

Characteristics of Carbanions:
1. Electron Configuration: Carbanions have an extra electron, which means that the carbon atom has a total of eight electrons in its valence shell, fulfilling the octet rule.
2. Stable Structures: Carbanions are relatively stable due to the presence of the negative charge on the electronegative carbon atom. The negative charge is delocalized over the carbon atom and adjacent atoms, providing stability.
3. Nucleophilic: Carbanions are excellent nucleophiles and participate in nucleophilic substitution reactions. The negative charge on the carbon atom makes it highly reactive towards electrophiles.
4. Solubility: Carbanions are often soluble in polar solvents due to their ionic nature.
5. Reactivity: Carbanions can react with electrophilic species, such as carbocations or other electrophiles, to form new chemical bonds.
6. Acidity: Carbanions can act as bases and are often formed by the deprotonation of a corresponding carbon acid.

Examples of Carbanions:
1. Methanide Ion (CH3-): In this carbanion, the negative charge is on the carbon atom, and the carbon atom is bonded to three hydrogen atoms.
2. Ethoxide Ion (C2H5-): In this carbanion, the negative charge is on the carbon atom, and the carbon atom is bonded to two hydrogen atoms and one ethyl group (C2H5).

Applications of Carbanions:
1. Organic Synthesis: Carbanions are widely used in organic synthesis to introduce new functional groups or create carbon-carbon bonds.
2. Polymerization: Carbanions are involved in the polymerization of certain monomers, such as styrene, to form polymers like polystyrene.

In conclusion, a carbon species carrying a negative charge on the carbon atom is known as a carbanion. Carbanions are stable, nucleophilic, and participate in various chemical reactions in organic chemistry.