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The chemical bond is the force that holds together the atoms that make up a chemical substance. These bonds can be of different types, depending on the particular atoms that are attached. On the one hand, there are covalent bonds, which are typical of molecular compounds. There are also ionic bonds, which occur in ionic compounds such as salts.
Generally speaking, we take it for granted that ionic compounds only contain ionic bonds. However, depending on the type of ion, there are ionic compounds in which a part of their structure is covalently bonded, giving rise to compounds with ionic and covalent bonds.
How compounds with ionic and covalent bonds are formed
Ionic compounds with covalent bonds are much more numerous than those that only form ionic bonds. In fact, any ionic compound that contains one or more polyatomic ions will necessarily be a covalently bonded ionic compound, since polyatomic ions, which are those formed by more than one atom, hold their atoms together through covalent bonds. .
Some of the most common polyatomic ions are:
| polyelectron anions | polyelectron cations |
| Sulfate (SO 4 2- ) | Ammonium (NH 4 + ) |
| Nitrate (NO 3 – ) | Phosphonium (PH 4 + ) |
| Carbonate (CO 3 2- ) | Hironium (H 3 O + ) |
| Hypochlorite (ClO – ) | |
| Peroxide (O 2 2- ) | |
| Cyanide (CN – ) |
There are many more, especially anions. Combining these ions with each other, or with any other monatomic ion of opposite charge, will result in an ionic salt that also possesses covalent bonds. Other common examples of this type of compound are made up of most medicines: these are usually organic salts that contain an anion consisting of a large organic molecule with negative carboxylate groups linked by ionic bonds to cations such as sodium or potassium.
As mentioned above, all the atoms of each of these ions are linked to each other by means of covalent bonds. These bonds can be polar or nonpolar; they can also be simple, double or triple.
As an example, the structure of the nitrate ion is shown in the following figure.
As can be seen, nitrogen is linked to three oxygens by means of covalent bonds: two of them are single covalent bonds, and the third corresponds to a double bond. In the presence of a suitable cation, the nitrate ion can form a salt in which said anion is bound to the cation via an ionic bond.
Examples of compounds with ionic and covalent bonds
The following list is a small sample of the large number of salts with covalent bonds that exist. However, it is a representative sample that highlights the most important characteristics of this type of compound:
| Ammonium nitrate (NH 4 NO 3 ) | Potassium sulfate (K 2 SO 4 ) | Potassium permananate (KMnO 4 ) |
| Lithium peroxide (Li 2 O 2 ) | Sodium carbonate (Na 2 CO 3 ) | Calcium phosphate (Ca 3 (PO 4 ) 2 ) |
| Sodium hypochlorite (CaClO) | Ammonium chloride (NH 4 Cl) | Phosphonium bromide (PH 4 Br) |
References
- The covalent bond . (2020, October 30). Retrieved from https://espanol.libretexts.org/@go/page/1854
- Valverde, M. (2021, May 25). How is matter formed? Types of chemical bonds, examples and characteristics . ZS Spain. https://www.zschimmer-schwarz.es/como-se-forma-la-materia-tipos-de-enlaces-quimicos-ejemplos-y-caracteristicas/
- Chang, R., & Goldsby, K. (2013). CHEMISTRY (11th ed.). McGraw-Hill Interamericana de España SL
