The atomic number of Carbon is 6 with an electronic configuration of 2,4. Hence, C has 4 electrons in its valence shell. C can lose or gain 4 electrons in order to gain stability. It cannot gain four electron as carbon atom having 6 protons is very small to handle 10 electron and it cannot donate electrons as it needs a lot of energy to do so. Hence, it cannot form C
4+
anion or C
4−
anion and thus forms a covalent bond.
1. Covalent bonds are formed by sharing of electrons. They don't have a free electron that is required for electricity transfer (electricity is the flow of free electrons), thus they are bad conductors.
2. Covalent compounds have low melting and boiling points because they have weak inter-molecular forces between bonds. Hence, less energy/temperature is needed to break the bonds.

Formation of Carbide Ion (C⁴-)

Carbon is known to primarily form covalent compounds due to its high electronegativity and small atomic size. However, under certain conditions, carbon can also form ionic compounds, such as the carbide ion (C⁴-).

1. Formation of carbide ion
- The carbide ion (C⁴-) is formed when carbon reacts with a metal. This reaction occurs because metals tend to have low ionization energy, meaning they readily lose electrons to form positive ions.
- In the case of carbon, it has a strong affinity for electrons and can gain four electrons to achieve a stable electron configuration similar to that of a noble gas (such as neon).
- These four electrons are gained from the metal atom, which loses four electrons to form a positive ion.
- This transfer of electrons results in the formation of an ionic compound between carbon and the metal, with the carbide ion (C⁴-) being negatively charged and the metal ion being positively charged.

2. Examples of carbide compounds
- One well-known example of a carbide compound is calcium carbide (CaC₂). In this compound, calcium (Ca) donates two electrons to each carbon atom, resulting in the formation of C⁴- ions.
- Another example is aluminum carbide (Al₄C₃), where aluminum (Al) donates three electrons to each carbon atom, leading to the formation of C⁴- ions.

3. Properties of carbide compounds
- Carbide compounds are generally hard and have high melting points.
- They have a crystalline structure and are often used in the production of abrasives, cutting tools, and other industrial applications.
- The carbide ion (C⁴-) is stable due to the complete filling of its valence shell with eight electrons.
- It is important to note that while carbon can form carbide ions in certain compounds, this does not mean that carbon forms ionic compounds with non-metals. In those cases, carbon still forms covalent bonds.

In summary, while carbon primarily forms covalent compounds, it can also form ionic compounds, such as carbide ions, when reacting with metals. The formation of carbide ions occurs through the transfer of electrons from the metal to carbon, resulting in the stability of both ions and the formation of an ionic bond. Carbide compounds have various industrial applications and possess specific properties due to their unique structure and bonding.