Atoms form covalent bonds by sharing their valence electron pairs in order to achieve a more stable electron configuration and attain a lower energy state. The concept of covalent bonding is based on the idea that atoms want to achieve a full outer electron shell, typically consisting of eight electrons, known as the octet rule.
When two atoms come together to form a covalent bond, they each contribute one or more electrons to a shared electron pair. By sharing electrons, both atoms can attain a more stable electron configuration resembling the noble gases, which have a full outer electron shell and are known for their high stability. This sharing of electrons allows both atoms to achieve a more favorable energy state, as it reduces the overall energy of the system.
For example, consider the formation of a covalent bond between two hydrogen (H) atoms. Each hydrogen atom has one valence electron in its outermost shell. By sharing their electrons, each hydrogen atom can achieve a full outer shell of two electrons, resembling helium (He). This results in a stable H2 molecule.
Similarly, in more complex molecules, atoms share electron pairs to satisfy the octet rule and achieve stability. For instance, in the formation of water (H2O), oxygen (O) shares two electrons with two hydrogen (H) atoms, resulting in a stable arrangement with oxygen having a full outer shell of eight electrons and each hydrogen atom having two electrons.
Covalent bonding allows atoms to share electrons in a way that benefits both atoms, leading to increased stability and a lower overall energy state for the system.