Atoms form chemical bonds to achieve a more stable and energetically favorable state. Atoms are composed of a positively charged nucleus, which contains protons and neutrons, surrounded by negatively charged electrons. The electrons are organized into different energy levels or orbitals around the nucleus.
Atoms seek to attain a more stable electron configuration, typically by either filling their outermost electron shell (valence shell) or achieving a completely filled or half-filled shell. This stability is achieved through the formation of chemical bonds, which involve interactions between the electrons of different atoms.
There are three primary types of chemical bonds:
Ionic Bonds: Ionic bonds occur between atoms with significantly different electronegativities, resulting in the transfer of electrons from one atom to another. This transfer leads to the formation of ions—positively charged cations and negatively charged anions. The opposite charges of the ions attract each other, creating an ionic bond. Examples include the bonding in sodium chloride (NaCl), where sodium donates an electron to chlorine, resulting in the formation of Na+ and Cl- ions.
Covalent Bonds: Covalent bonds occur when atoms share electrons in order to complete their valence shells. This sharing of electrons allows both atoms to achieve a more stable electron configuration. Covalent bonds are typically formed between nonmetallic elements. For instance, in a molecule of water (H2O), each hydrogen atom shares a pair of electrons with the oxygen atom, forming covalent bonds.
Metallic Bonds: Metallic bonds occur between metal atoms, where valence electrons are not tightly associated with any particular atom and are free to move throughout the entire metal lattice. This creates a "sea" of delocalized electrons that hold the metal ions together. Metallic bonds are responsible for the characteristic properties of metals, such as malleability and electrical conductivity.
These different types of chemical bonds allow atoms to achieve greater stability by filling or completing their valence shells, leading to a lower overall energy state. The formation of chemical bonds enables atoms to become more tightly connected, forming molecules or compounds that possess distinct properties and behaviors.