The valency of an atom refers to its ability to form chemical bonds with other atoms. Carbon is an element that can exhibit different valencies, typically 2 and 4, depending on the specific compounds it forms.
The valency of carbon depends on its electron configuration. In its ground state, a carbon atom has 6 electrons. The electron configuration of carbon is 1s^2 2s^2 2p^2. This configuration means that carbon has 4 valence electrons located in its outermost electron shell, specifically in the 2s and 2p orbitals.
When carbon forms compounds, it tends to either gain or lose electrons to achieve a stable electron configuration. Carbon can share electrons with other atoms to form covalent bonds, allowing it to achieve a stable configuration with 8 electrons in its outer shell, following the octet rule.
Carbon's valency of 4 arises when it shares its 4 valence electrons with other atoms. It can form four covalent bonds by sharing its electrons with other atoms that have the necessary number of electrons to complete their own outer shells.
For example, in methane (CH4), carbon forms four single covalent bonds with four hydrogen atoms, sharing one electron from each hydrogen atom to complete its octet. Each bond involves one electron from carbon and one electron from hydrogen, resulting in a total of 4 shared electron pairs and 4 covalent bonds around carbon.
On the other hand, carbon can also exhibit a valency of 2 in certain compounds. This occurs when carbon forms double or triple bonds, sharing 2 or 3 pairs of electrons with other atoms, respectively. In compounds such as ethene (C2H4) or acetylene (C2H2), carbon forms double and triple bonds, respectively, resulting in a valency of 2.
In summary, the valency of a carbon atom can be 2 or 4 depending on the type of compound it forms. It can form four covalent bonds by sharing its 4 valence electrons, or it can form double or triple bonds by sharing 2 or 3 pairs of electrons, respectively.