Types of Chemical Bonds: Ionic, Covalent and Its Properties

Types of Chemical Bonds: The matter is made up of the same or different kinds of elements. Under normal conditions, no other element exists as an independent atom in nature, except noble gases. Instead, atoms of the same or different kinds of elements combine to form molecules.
Molecules are the aggregates of atoms held together by the forces of attraction, called chemical bonds, and behave as a single entity.

Definition of Chemical Bond

The phenomenon of the union of two or more atoms involving the redistribution of electrons so that each atom involved in bonding acquires a stable electronic configuration to gain stability is known as chemical bonding.

What are Chemical Bonds?

All the atoms complete their duplet or octet by acquiring the nearest noble gas electronic configuration to attain stability. It can be achieved by the formation of chemical bonds between atoms. Do you know how?

An atom can form chemical bonds in three ways,
(a) By losing one or more electrons to another atom.
(b) By gaining one or more electrons from another atom.
(c) By sharing one or more electrons with another atom.

The two modes of attaining the electronic configuration of the nearest noble gas give rise to four types of bonds.

Types of Chemical Bonds

There are \(4\) types of chemical bonds and they are:

1. Ionic or electrovalent bond  
2. Covalent bond
3. Hydrogen bond
4. Polar covalent bond

Ionic Bond(or)Electrovalent Bond

When a metal reacts with a non-metal, the transfer of valence electrons from one atom to another form’s compounds, the bond formed by the complete transfer of one or more electrons from the valence shell of one atom to another is called an ionic or electrovalent bond.

The compounds containing ionic bonds are called ionic compounds, as ions are their constituent particles. The number of electrons lost or gained by the atom during the bond formation is called its electrovalency.

When forming an ionic bond between a metal and a non-metal, the metal atom gives one or more electrons to the non-metal and becomes a positively charged cation. The non-metal gains electrons and becomes a negatively charged anion. The positive and negative ions attract one another. The vital force of attraction developed between the oppositely charged ions is known as an ionic bond. The compounds formed by ionic bonds are called ionic compounds because they are made up of oppositely charged ions. Let us take an example showing the formation of ionic compounds.

Formation of Potassium Chloride, \({\text{KCl}}\)
Potassium reacts with chlorine to form ionic compounds potassium chloride \(\left({{\text{KCl}}} \right).\) In this compound, potassium is a metal, and chlorine is a non-metal. The atomic number of potassium is \(19,\) and so, its electronic configuration is \(2,8,8,1.\) It has only one electron in its outermost shell. Hence, the potassium atom donates one electron to a chlorine atom to form a potassium ion, \({{\text{K}}^ + }.\)
\({\rm{K – }}{{\rm{e}}^{\rm{ – }}} \to {{\rm{K}}^{\rm{ + }}}\,{\rm{Potassium}}\,{\rm{atom – Electron = Potassium}}\,\,{\rm{ion}}\)
The atomic number of chlorine is \(17,\) and so its electronic configuration is \(2,8,7.\) It requires only one electron to achieve the nearest noble gas configuration of argon. Hence, it accepts an electron from a potassium atom to form a chloride ion, \({\text{C}}{{\text{l}}^ – }.\)
\({\rm{Cl – }}{{\rm{e}}^{\rm{ – }}} \to {\rm{C}}{{\rm{l}}^{\rm{ – }}}\,{\rm{Chlorine}}\,{\rm{atom + Electron = Chlorine}}\,\,{\rm{ion}}\)

When potassium reacts with chlorine, it forms potassium chloride as shown:

The above reaction shows that due to opposite charges, potassium ion \({{\text{K}}^ + }\) and chloride ion \({\text{C}}{{\text{l}}^ – }\) are held together by the electronic force of attraction to form \({{\text{K}}^ + }{\text{C}}{{\text{l}}^ – }.\)
The potassium ion resembles the argon gas configuration, and the chloride ion also corresponds to the argon gas configuration. We can show the formation with the help of a diagrammatic sketch as

Properties of Ionic Bond

(a) Physical State: Most of the ionic compounds are crystalline solids. They are hard because of strong electrostatic forces of attraction between two oppositely charged ions. As a result, they are brittle and break into pieces easily.
(b) Solubility: They are soluble in water but are insoluble in organic solvents such as benzene, ethers, etc. The solubility of ionic solids in water is due to the polar nature of water molecules.
(c) Melting Point and Boiling Point: They have a high melting point and boiling point. It requires a lot of energy to break the strong electrostatic force of attraction between the oppositely charged ions to form ions.
(d) Colour in the Flame: Each ionic compound imparts colour to the flame when brought into the flame
(e) Electrical Conductivity: Ionic compounds in a solid-state do not conduct electricity because the oppositely charged ions are held together by strong electrostatic forces of attraction and are not to move. But when dissolved in water, the ionic compounds dissociate to produce ions in the solution. Since the ions can conduct electricity, the ionic compounds conduct electricity in an aqueous or molten state.
(f) High Density: Ionic compounds are generally heavier than water.
(g) Space Isomerism: The ionic bond is non-directional. Ionic compounds do not show space isomers or stereoisomers.

Covalent Bond

The chemical bond formed between two atoms due to the mutual sharing of electrons is called a covalent bond. This is because the atoms share only their outermost electron so that each atom gets the stable electron arrangement of inert gas. The number of electrons shared between the atoms is called its covalency.
A covalent bond can also be formed between two atoms of the same non-metal. For example, when two chlorine atoms combine, it includes a chlorine molecule sharing an electron between chlorine atoms.

When a non-metal reacts with another non-metal, both share electrons to form a covalent bond. The number of shared electron pairs constitutes the covalent bond. The covalent bonds are of three types, namely,

1. Single covalent bond
2. Double covalent bond
3. Triple covalent bond

Single Covalent Bond

A single covalent bond is formed when one pair of electrons is shared between two atoms.
OR
A single covalent bond is formed by the mutual sharing of one electron pair between two atoms. In a single covalent bond, each atom contributes one electron for sharing. It is represented by a single line \(\left( – \right)\) between the two atoms sharing electrons.

Formation of Chlorine Molecule 

Chlorine contains seven electrons in the valence shell, and it requires one electron to complete its octet. Therefore, it may share one electron with another chlorine atom to form a chlorine molecule as shown below:

Formation of a Methane Molecule \(\left( {{\text{C}}{{\text{H}}_4}} \right)\):
A carbon atom has four electrons in its outermost shell (valence shell). It shares its valence electrons with those of four \({\text{H}}\) atoms. Thus, an atom of carbon forms four single covalent bonds with four \({\text{H}}\) atoms

Pictorially, a methane molecule represents as

In a methane molecule, the carbon atom and each of the four H atoms acquire the stable electronic configurations of neon and helium. In methane, we have four carbon-hydrogen \(\left({{\text{C}} – {\text{H}}} \right)\) single bonds. Thus, a methane molecule has four pairs of shared electrons.

Double Covalent Bond

A double covalent bond formed by the mutual sharing of two-electron pairs between two atoms. In a double covalent bond, each atom contributes two electrons for sharing. It represents by a double line \(\left( = \right)\) between the two atoms sharing electrons.

Formation of an Ethylene Molecule \(\left({{{\text{C}}_2}{{\text{H}}_4}} \right)\)- The formation of an ethylene molecule \(\left( {{{\text{C}}_2}{{\text{H}}_4}} \right),\) each of the two \({\text{C}}\) atoms combines with two \({\text{H}}\) atoms to form two single covalent bonds. The remaining two electrons of each \({\text{C}}\) atom form a double bond between the two \({\text{C}}\) atoms.

Formation of Carbon Dioxide Molecule \(\left({{\text{C}}{{\text{O}}_2}} \right)\):
Carbon contains four electrons in the valence shell, and it requires four electrons to complete its octet, while oxygen has six electrons in the valence shell, and it requires two electrons to complete its octet. Carbon may complete its octet by sharing two electron pairs with two oxygen atoms forming two double bonds. The formation of carbon dioxide \(\left({{\text{C}}{{\text{O}}_2}} \right)\)molecule shown below:

Triple Covalent Bond

A triple covalent bond formed by the mutual sharing of three electron pairs between two atoms. In a triple covalent bond, each atom contributes three electrons for sharing. It represents by a triple line \(\left( \equiv \right)\) between the two atoms sharing electrons.

Formation of an Acetylene Molecule \(\left( {{{\text{C}}_2}{{\text{H}}_2}} \right)\):
In an acetylene molecule, two \({\text{C}}\) atoms combine with two \({\text{H}}\) atoms. Each \({\text{C}}\) atom shares three of its valence electrons with the other \({\text{C}}\) atom. Thus, one electron of each \({\text{C}}\) atom is shared with one electron of an \({\text{H}}\) atom.

Thus, in a molecule of acetylene, there is a triple covalent bond between the two \({\text{C}}\) atoms, and each \({\text{C}}\) atom is joined to one \({\text{H}}\) atom by a single covalent bond. Thus, pictorially, a molecule of acetylene may represent as

Properties of Covalent Compounds

(a) Physical State: Generally, covalent compounds are liquids or gases because of a weak covalent force of attraction between their molecules. Only a few of them are solids.
(b) Solubility: They are insoluble in water but are soluble in organic solvents. However, some covalent compounds such as sugar, urea, glucose, ammonia, hydrogen chloride, etc., are soluble in water.
(c) Melting Point and Boiling Point: They have a low melting point and boiling point. It requires only a tiny amount of energy to break the weak covalent force of attraction between the molecules of covalent compounds.
(d) Electrical Conductivity: The covalent compounds do not conduct electricity because they do not contain ions. However, covalent compounds like ammonia, hydrogen chloride conduct electricity when dissolved in water. It is because hydrogen chloride chemically reacts with water to form hydrochloric acid-containing ions.

Hydrogen Bond

A hydrogen bond can be defined as the attractive force which binds the hydrogen atom of one molecule with the electronegative atom of another molecule.

When hydrogen is bonded to highly electronegative atoms such as fluorine or oxygen, or nitrogen by a covalent bond, the electron pair is attracted towards the electronegative atom so strongly that a dipole results. When several such molecules are brought nearer to each other, the positive end of one molecule and the negative end of the other molecule will attract each other, and a weak electrostatic force will develop. Thus, these molecules associate together to form a cluster of molecules.

Polar Covalent Bond

The molecules which have two oppositely charged poles are called polar molecules, and the bond is said to be a polar covalent bond.

A covalent bond in which the electron pair is shared unequally between the two atoms. The bonded atoms that acquire partial positive and partial negative charges are called polar covalent bonds.

The polar covalent bond is generally formed between the two atoms, which have a difference in electronegativity greater than zero or less than \(1.7.\) Therefore, the molecule in which polar covalent bonds bond the atoms together is called a polar molecule.

Summary

The bond formed by sharing electrons is called covalent bonding, and the bond formed by the transfer of one or more electrons is called an ionic bond. The salt we use for preservatives, the oxygen we inhale to the exhalation of carbon dioxide consists of compounds containing different chemical bonds. Hence, to summarise, it is indeed needless to say that without chemical bonds, our existence is impossible.

Frequently Asked Questions on Chemical Bonds

Q.1. Why do ionic compounds have high melting points?
Ans: Ionic compounds have high melting and boiling points due to the vital force of attraction between ions.

Q.2. Write three properties of covalent compounds.
Ans: (i) These compounds have low melting and boiling points compared to ionic compounds due to weak intermolecular forces.
(ii) These generally do not conduct electricity when present in pure form.
(iii) These compounds are generally insoluble in water. Only a few covalent compounds that make hydrogen bonding with water are soluble in it.

Q.3. What are the four types of bonds in chemistry?
Ans: The four chemical bonds present in chemistry are covalent, hydrogen bonds, van der Waals interactions, and ionic or electrovalent bonds.

Q.4. Which chemical bonds are the strongest?
Ans: The strongest chemical bond is the covalent bond. These formed between two atoms due to the mutual sharing of electrons. A common example of a covalent bond is water, in which both the hydrogen atoms and the oxygen atom share electrons.

Q.5. Explain the formation of the ammonia molecule.
Ans: Ammonia is formed by sharing three electrons of nitrogen with three hydrogen atoms to form three single bonds. The formation of the ammonia molecule is shown below:

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