Final answer:
In covalent bonds, electrons are shared between atoms, which can result in either nonpolar molecules, if the sharing is equal, or polar molecules if one atom has a stronger pull on the electrons. A coordinate covalent bond is a type of covalent bond where both electrons come from the same atom. These bonds are crucial for the formation of molecules consisting of nonmetals or semimetals.
Step-by-step explanation:
In a covalent bond, the electrons are shared between atoms. This type of bond occurs when two nonmetal atoms unite, where the shared electrons are attracted to the nuclei of both atoms, thereby forming a molecule. For a basic covalent bond, each atom contributes one electron to form a pair. When these shared electrons are balanced, meaning they are attracted equally by the two atoms' nuclei, the resulting molecule is described as nonpolar. However, in many cases, one atom exerts a greater pull on the electrons than the other, leading to polar covalent bonds.
Additionally, a special type of covalent bonding is known as a coordinate covalent bond or dative bond, where both shared electrons originate from the same atom. In molecules where covalent bonding is the primary form of chemical bonding, the electrons tend to move about without a permanent transfer, similar to how neighbors might share resources without losing ownership.
According to the octet rule, multiple covalent bonds, such as double or triple bonds, may form if necessary to ensure each bonded atom attains a full valence shell, except in the case of hydrogen and helium. Covalent bonds are fundamental to the structure and function of molecules, particularly those consisting of semimetals or nonmetals.