Key difference - ionic vs. covalent compounds
Almost all compounds in chemistry can be roughly divided into ionic and covalent compounds . They differ from one another based on the type of bond between the atoms that are involved in the formation of a molecule / compound. As their names suggest, ionic bonds are made up of ionic bonds and covalent bonds are made up of covalent bonds. Ionic bonds occur between two species that are electrostatically attracted to each other, while covalent atoms covalently bond by sharing electrons between their outer shells . This is the main difference between ionic and covalent compounds. In general, metallic elements tend to form ionic bonds, and non-metallic elements eventually form covalent bonds.
What are ionic compounds?
As mentioned above, ionic compounds are the result of electrostatic forces between atoms that are attracted to one another due to the possession of opposite electrical charges. Each element tries to achieve a stable electronic configuration on the outer shell (electronic configuration of the noble gases). An electronic noble gas configuration prevents atoms from carrying out further reactions because they are already stable. Therefore, elements in nature that are not electronically stable tend to donate extra electrons or accept the missing number of electrons to achieve the tightest noble gas configuration. Ions are formed according to this principle. Atoms that tend to give up their extra electrons in order to achieve a stable electronic configuration end up being positively charged (due to the loss of negatively charged electrons) and these are known as " cations ". Similarly, as atoms pick up electrons to complete the final shell configuration, they become negatively charged (due to the increase in negatively charged electrons) and these are known as " anions ". Therefore, by definition, ionic bonds are formed between anions and cations .
In general, atoms that form ionic compounds are surrounded by oppositely charged atoms. Therefore, instead of forming individual molecular units, they group into clusters called “crystals”. Therefore, the ionic compounds tend to be inherently solid and they usually have very high melting points because the ionic bonds are quite strong; in fact, it is the strongest type of chemical bond there is. In liquid form, they become excellent conductive materials because the ions can migrate freely. Ions can be atomic or molecular in nature. ie CO 3 2- is a molecular anion. In the case of H + (hydrogen) which is cation, the compound is called an acid, and if the anion is OH - it is called a base. Some examples of ionic compounds are NaCl, MgCl 2 , etc.
What are covalent bonds?
These are compounds that are formed by covalently bound atoms. Covalent bonds are much weaker than ionic bonds and therefore most covalent bonds exist in the gas phase. As mentioned above, atoms must form bonds in order to achieve a stable electronic configuration. And the third way to achieve this (besides donating and accepting electrons, as mentioned with ionic bonds) is by sharing electrons.
In this method, both atoms involved in the formation of the compound share the required number of electrons (usually with a 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 get very close for the orbital overlap before the electron distribution takes place. Therefore, in this case, no atom is electrically charged, but remains neutral. The overlap can be linear or parallel. If it is directional and linear, the bond type is referred to as a “σ bond”, otherwise it is referred to as a “π bond”. Furthermore, this sharing of electrons can take place between similar types of atoms as well as between different types of atoms. When the atoms involved are similar, the resulting compound is referred to as a "diatomic molecule". H 2 O, CO 2 , etc. are some common examples.
Difference between ionic compounds and covalent compounds
Ionic compounds consist of ionic bonds in which the atoms are electrostatically attracted to one another.
Covalent bonds consist of covalent bonds in which the electrons are shared between the atoms involved in the formation.
Ionic compounds arise from the interaction between cations and anions.
Covalent bonds are created through the interaction of neutral atoms.
Ionic bonds are the strongest type of chemical bond and therefore most compounds with very high melting points stay solid.
In contrast, covalent bonds are quite weak and therefore most of the compounds exist in the gas phase.
Ionic compounds become a highly conductive medium in liquid form.
Covalent bonds are not good electrical conductors.