A chemical bond is a bond formed between two ions, atoms and molecules which helps in the formation of various types of chemical compounds. Various kinds of bonds may be formed due to electrostatic forces (occurs between charges opposite in nature). It is also seen in ionic bonds. Generally, the bonds are formed by sharing of electrons (seen generally in covalent bonds).
The strength of bonds varies depending upon their type. Strong bonds, also known ad primary bonds include covalent, ionic and metallic bonds. Weak bonds are also known as secondary bonds. Examples of secondary bonds include dipole-dipole interactions, hydrogen bonds and the London forces.
Covalent bonds are formed as a result of the linking of atoms that share pairs of electrons. Atoms covalently bond with each other to attain greater stability, through the formation of a complete shell of electrons. Exchanging of electrons takes place which results in filling up of electrons in the outermost shell of the atoms and ultimately gaining stability.
According to the octet rule, the atoms in a main group of elements need to bind so that all of the atoms contain eight electrons in their outermost shell/valence shell, and thereby attain the noble gas electronic configuration. In the case of covalent bonds, the atoms generally share their electrons so that the atoms involved in covalent bonding follow the Octet rule and attain stability by achieving the nearest noble gas configuration.
Different atoms combine with each other in different ways. Sharing of electrons and attaining noble gas configuration by the virtue of octet rule in this way results in the formation of covalent bonding. These kinds of properties are shown by nonmetals and H+ metals generally need at least four electrons to attain noble gas configuration, which is almost impossible due to the involvement of high energy.
Based on the number of pairs of electrons that atoms share between them, there are three types of covalent bonds:
- Single Bond: One electron pair is shared between the atoms.
- Double Bond: Two electron pairs are shared between the atoms.
- Triple Bond: Three electron pairs are shared between the atoms.
Ionic bond, also known as ‘electrovalent bond’ is generally formed by the force of electrostatic attraction (due to the oppositely charged ions forming a chemical bond). These kinds of bonds are formed when the electrons from the valence shell of one atom are permanently transferred to another atom. The atom which loses electrons converts into positive charge ions (cations) and the ones which gain electrons become negatively charged ions (anions). Ionic bonding is generally seen between alkali metals, alkali earth metals and non-metals.
In ionic crystalline solids, the electrostatic forces of attraction between opposite charges and the force of repulsion between similar charges manage the ions in a way that each positive ion gets surrounded by negative ions and vice versa. The ions are arranged such that the positive and negative charges are placed alternately and they tend to balance one another, resulting in the overall charge of the entire substance being zero. The electrostatic force cannot be ignored here. Compounds involving ionic bonds are generally hard and non-volatile in nature. There are three types of ionic bonds formed:
- Sodium chloride
- Potassium phosphate
- Magnesium phosphate
Difference Between Covalent and Ionic Bonds:
Ionic bonds and covalent bonds are the two main types of chemical bonds. The properties shown by these two bonds are quite different from one another. Ionic bonds are formed by the transfer of electrons permanently from one atom to another while in the case of covalent bonds, sharing of electrons between the two atoms takes place.