Difference Between Ionic and Covalent Compounds

Main Difference – Ionic vs. Covalent Compounds

Almost all the compounds in Chemistry can be broadly categorized into Ionic and Covalent Compounds. They differ from each other due to the bonding type between the atoms that take part in making a molecule/ compound. As their names suggest, ionic compounds are made of ionic bonds, and covalent compounds are made of covalent bonds. Ionic bonds occur between two species which are electrostatically attracted towards each other, whereas covalent atoms bond covalently through the sharing of electrons between their outer shells. This is the main difference between Ionic and Covalent Compounds. In general, metallic elements tend to form ionic compounds, and non-metallic elements end to form covalent bonds.

What are Ionic Compounds

As mentioned above, Ionic Compounds are a result of electrostatic forces between atoms that get attracted towards each other due to the possession of opposite electrical charges. Each element tries to accomplish a stable electronic configuration at the outer shell (electronic configuration of the noble gasses). Having a noble gas electronic configuration prevents atoms from further reactions as they are already stable. Therefore, elements in nature which are not electronically stable, tend to give away any extra electrons or accept the missing number of electrons in order to achieve the closest noble gas configuration. Ions are formed by this principle. Atoms which tend to give away their extra electrons to attain stable electronic configuration end up being positively charged (due to the loss of negatively charged electrons) and these are called, “cations.” Similarly, when atoms accept electrons to complete the final shell configuration they become negatively charged (due to the increase in negatively charged electrons) and these are called, “anions.” Therefore by definition, ionic bonds are formed between anions and cations.

In general, atoms that form ionic compounds gets surrounded by the oppositely charged atoms. Therefore, they group into clusters which are called ‘crystals,’ rather than forming single molecular entities. Hence, the ionic compounds tend to be solid in nature, and they usually have very high melting points as the ionic bonds are quite strong; in fact it is the strongest type of chemical bond that exists. In liquid form, they become excellent conducting materials as the ions are free to travel. Ions can be atomic or molecular in nature. i.e. CO₃^2-is a molecular anion. In the case of H⁺ (Hydrogen) being the cation, the compound is called an acid and when the anion is OH^– it is called a base. Few examples of ionic compounds are NaCl, MgCl_2, etc.

What are Covalent Compounds

These are compounds formed by covalently bound atoms. Covalent bonds are much weaker than ionic bonds and, therefore, most of the covalent compounds exist in the gaseous phase. As mentioned above, atoms need to form compounds in order to attain a stable electronic configuration. And the third way of obtaining this (apart from giving away and accepting electrons as mentioned in the case of the ionic bonds) is through the sharing of electrons.

In this method, both atoms taking part in the formation of the compound get to share the required number of electrons (usually with one donor atom and an acceptor atom looking for the same amount of electrons) in a common overlapped orbital space. It is important that the atoms come into close proximity of each other for the orbital overlap before the electron sharing takes place. Therefore, in this case, neither atom will be electrically charged but will remain neutral. The overlapping can take place in a linear fashion or in a parallel manner. When it is directed, and linear the bond type is called a “σ bond” and in the other case is a “π bond.” Furthermore, this sharing of electrons can take place between similar type of atoms as well as different types of atoms. When the involved atoms are similar, the resulting compound is called a ‘di-atomic molecule.’ H₂O, CO_2, etc. are some common examples.