An ionic bond is defined as that bond between a metal and a non-metal which is responsible to hold the oppositely charged ions by the strong electrostatic force of attraction. The bond formed as a result of the transference of electrons from the outermost shell of metal to the outermost shell of a non-metal is alternatively known as an electrovalent bond.
There are two essential factors for Ionic Bond formation: 1. the metals participating in an ionic bond formation should have low Ionization Potential and 2. the non-metals participating in an ionic bond formation should have high Electron Affinity. Ionization Potential is the energy required to remove an electron from the outermost shell of an isolated gaseous atom. And finally, electron affinity is defined as the energy released in addition of an electron to the outermost shell of an isolated gaseous atom.
What are Electrovalent Compounds?
The chemical compounds formed as a result of the transfer of electrons from the outermost shell of metal to the outermost shell of a non-metal are called electrovalent compounds.
What are the Properties of Ionic or Electrovalent Compounds?
1. Ionic Compounds are Hard Solids.
This is because their constituent particles are ions which are held by the strong electrostatic force of attraction and hence they cannot be separated easily.
2. Ionic Compounds Have A High Melting Point and High Boiling Point.
They are non-volatile solids. As in these compounds, ions are held by the strong electrostatic force of attraction, so a large amount of energy is required to overcome these forces of attraction between the ions.
3. Ionic Compounds Do Not Conduct Electricity in Their Solid-State.
However, they can conduct electricity in their fused, molten and in their aqueous solution. In solid-state, they do not conduct electricity as the ions are not free but held by the strong electrostatic force. But infused or molten state, these forces of attraction get weakened and thus the ions become free to conduct electricity. In aqueous solution, the high dielectric constant overcomes the strong electrostatic force of attraction, thus making the ions free to conduct electric current.
4. Ionic Compounds Act as Strong Electrolytes.
As on dissolving in water, ionic compounds allow the passage of electric current through them due to the presence of free ions.
5. Ionic Compounds are Soluble in Water but Insoluble in Organic Solvents like Benzene and Phenol.
As water has maximum dielectric constant, therefore it decreases the force of attraction between the ions and thus it forms free ions and hence they dissolve in water. But in organic solvents like Phenol, as the dielectric constant is minimum, it increases the force of attraction making the ions more strongly held by the electrostatic force which makes the compounds insoluble.
6. On passing an electric current through fused, molten and aqueous solution of electrovalent compounds, the ions dissociate and migrate towards electrodes.
7. Ionic compounds undergo fast reactions in their aqueous solution.
What is the Principle of Ionic or Electrovalent Compounds Formation?
An Ionic compound is formed when atoms of metals from Groups 1 to 3 in the periodic table loses electrons to the atoms of the non-metals from Groups 5 to 7 in the periodic table to complete their stable electronic configuration according to Duplet or Octet rule. The protons of these atoms remain constant during these transfers of electrons.
What is the Duplet Rule?
Elemental atoms generally lose, gain, or share electrons with other atoms in order to achieve the same electron structure as the nearest rare gas with two electrons in the outer level.
What is the Octet Rule?
Elemental atoms generally lose, gain, or share electrons with other atoms in order to achieve the same electron structure as the nearest rare gas with eight electrons in the outer level.
Example: Sodium Chloride Formation by Ionic Bond?
There is only one electron in the outermost shell of Sodium (Na) atom and if it loses that electron from its outermost shell i.e. the M shell then the L shell becomes the outermost shell and it has a stable octet. There are eleven protons in the nucleus of this atom but the number of electrons has become ten, this gives the sodium atom a positive charge and creates a sodium cation Na+. Whereas, on the other hand, there are seven atoms in the outermost shell of the Chlorine (Cl) atom then it needs one more electron to complete its octet. If Sodium and Chlorine reacted then the electron lost by sodium would be taken by Chlorine. After this process, the chlorine atom would have a negative charge, because it would have seventeen protons in its nucleus and there would be eighteen electrons in its K, L and M shells. This gives the Chlorine atom a negative charge. Hence, the negatively charged Chlorine and positively charged Sodium creates an Ionic bond or an Electrovalent compound called Sodium Chloride, commonly known as Common Salt.
()
What are Cations and Anions
Ionic bonds involve a cation and an anion. The bond is formed when an atom, typically a metal, loses an electron or electrons and becomes a positive ion, or cation. Another atom, typically a non-metal, is able to acquire the electron(s) to become a negative ion or anion. Another example of an ionic bond is the formation of sodium fluoride, NaF, from a sodium atom and a fluorine atom. In this reaction, the sodium atom loses its single valence electron to the fluorine atom, which has just enough space to accept it. The ions produced are oppositely charged and are attracted to one another due to electrostatic forces.
What are the Differences between Electrovalent Compounds and Covalent Compounds?
-
Ionic compounds are solids whereas covalent compounds are liquids or very soft waxy solids.
-
Ionic compounds have a high melting point and high boiling point but covalent compounds have a low melting point and low boiling point.
-
Ionic compounds are soluble in water but covalent compounds are soluble in organic solvents like Benzene and Phenol.
-
Ionic compounds are insoluble in organic solvents like Benzene and Phenol but covalent compounds are insoluble in water.
-
Ionic compounds undergo fast reactions whereas covalent compounds proceed with slow reactions.
-
Ionic compounds conduct electricity in the molten, fused or aqueous solution due to the presence of free ions whereas covalent compounds do not conduct electricity because the ions are absent and only molecules are present.
What are Oxidation and Reduction?
Oxidation is the process of loss of electrons. It takes place at the anode. During oxidation, anion losses electrons and get converted to a neutral particle.
Reduction is the process of gain of electrons. It takes place at the cathode. During reduction, cation gains electrons and get converted to a neutral particle.