Chapter 4: Molecular Compounds

4.1 Covalent Bonds

Covalent bonds are a fundamental type of chemical bond where two atoms share one or more pairs of electrons. This sharing allows each atom to achieve a stable electron configuration, often resembling that of the nearest noble gas.

• Covalent Bond: A bond formed by the sharing of electrons between two nonmetal atoms.

• Molecule: A group of atoms held together by covalent bonds, forming a distinct entity.

• Main group elements tend to react to achieve eight valence electrons (the octet rule), except hydrogen, which achieves two.

• Nonmetals achieve an octet by sharing electrons in covalent bonds.

Example: The hydrogen molecule (H2) forms when two hydrogen atoms share their 1s electrons, resulting in a stable electron pair between them. This can be represented as H–H, H:H, or H2.

• Bond Length: The optimal distance between the nuclei of two bonded atoms, where attractive and repulsive forces are balanced.

• Other diatomic elements (e.g., N2, O2, F2, Cl2, Br2, I2) also form by sharing electrons.

Additional info: Covalent bonds differ from ionic bonds, where electrons are transferred rather than shared. Covalent bonds typically occur between nonmetals, while ionic bonds form between metals and nonmetals.