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Ionic bonding - Formation, Conditions, Properties, Practice problems & FAQs

Ionic bonding - Formation, Conditions, Properties, Practice problems & FAQs

Assume you are in class and your teacher has instructed you to bring two pens. However, you only have one pen and are concerned that your teacher will not allow you to sit in class. What are you going to do in this situation? Ask for help? One of your classmates has an extra pen and he gives it to you. Will you be saved now? Of course, yes. Because now you are satisfying the condition asked by your teacher. In this process, you will become friends with that classmate for helping you.

The same things happen in chemistry too and here, we call it by the name ionic bonding which can be defined as the chemical connection in which one atom loses valence electrons and another atom gains these valence electrons thereby attaining a stable noble gas configuration by converting them to ions. The attractive electrostatic interactions between two ions of opposite charge form an ionic bond. 


Now, let’s try to understand ionic bonding in more detail.

Ionic bonding is a form of chemical connection in which one atom loses valence electrons and another atom gains these valence electrons attaining +ve and -ve charges respectively. The attractive electrostatic interactions between two ions of opposite charge form an ionic bond. For both atoms involved, this exchange results in a more stable noble gas electrical state

Table of content:

  • Ionic bond
  • Why are ionic bonds formed?
  • Favourable conditions for the formation of ionic bond
  • Properties of Ionic compounds

Ionic bond

Electrovalent bonds or ionic bonds are formed when electrons are transferred from atoms of one element to atoms of another element, producing positive and negative ions thereby attaining the nearest noble gas configuration (octet rule). Due to the formation of charged ions, there exists an electrostatic force of attraction between positively charged cation and negatively charged anion which results in the formation of a bond known as an ionic bond. They are also known as electrovalent bonds. Since it is formed by the transfer of electrons it is non-directional.

For example; 


Why are ionic bonds formed?

Let’s try to understand this with the help of an example.

We know,

Electronic configuration of = 2, 8, 1

Electronic configuration of = 2, 8, 7

Electron lost by to attain nearest stable electronic configuration = 1

Electron gained by to attain nearest stable electronic configuration = 1

Now, when these elements are gaining and losing electrons, they are doing it to attain nearest stable electronic configuration and are becoming charged in the process which due to electrostatic force of attraction results in the formation of ionic bond and form stable molecules i.e.,  

So, we can say that bonding is a way of reducing the energy of an atom to attain stability.

The atom which loses electron is called an electropositive atom and the atom which gains electron is called an electronegative atom.

; Na is electropositive atom

; Cl is electronegative atom

Favorable conditions for the formation of an ionic bond

  • Low Ionization enthalpy: Atoms having low ionization enthalpy will form cations

easily by losing electrons. In the periodic table, ionization energy increases along the period and decreases down the group.

Example: an atom with 1 electron in the outermost shell loses an electron and complete its octet which results in the formation of a cation.

  • Higher electron gain enthalpy: Atoms having high electron gain enthalpy gain electrons easily and readily form an anion. Thus, Ionic bonds can be formed easily. 

Example: atom with 7 electrons in the outermost shell gains an electron and completing its octet and forms anions readily 

  • Higher lattice energy: Energy required to completely convert one mole of a solid ionic compound into its gaseous constituent ions.

Charge and size are the deciding factors for the formation of ionic bonds:

  • Larger the magnitude of the charge on the ions, greater will be the attractive force and consequently, higher is the value of lattice energy and stronger will be the ionic bond. 

 

Where, = Charge on cation and = Charge on anion

  • Smaller the size of ions, the lesser the internuclear distance and greater will be an interionic attraction. Hence, more will be the value of lattice energy and stronger will be the ionic bond. 

Here,

Where,

Properties of Ionic compounds

  • Soluble in polar solvent
  • High melting and boiling point
  • Conduct electricity in aqueous and molten state
  • Exhibit isomorphism and polymorphism
  • Formed only between highly electropositive metals and nonmetals.
  • Ionic bonds are the strongest among all the bonds

Practice problems: 

Question: Which shows the highest lattice energy?

(A)
(B)  
(C)
(D)

Answer: We know that the lesser the internuclear distance, the greater will be an interionic attraction. Hence, more will be the value of lattice energy.

Therefore among , , and , ions have the smallest size so the internuclear distance is less hence lattice energy is highest for crystals.

Answer: Option ©

Question: Show electron transfer between and atoms to form cations and anions resulting in ionic bond formation.

Answer: We know,

Electronic configuration of = 2, 8, 3

Electronic configuration of = 2, 5

It is clear that need 3 more electrons to attains nearest stable noble gas configuration and on the other hand has 3 extra electrons. So, can lose 3 electrons to become and these 3 electrons will be gained by to become . Due to electrostatic forces of attraction between and , they will form ionic bond and will become .

Question: Why lattice energy decreases down the group?

Answer: The lattice energy decreases as we move down the group. This is due to the fact that as ion sizes increase, so does the distance between their nuclei. As a result, the attraction between them decreases, and less lattice energy is released during the process.

Answer: 

Question: What are the differences between covalent and ionic bonds?

Answer:

Covalent bonds Ionic bonds
Formed between two similar electronegative non-metals Formed between a metal and a non-metal
Have a definite shape Have no definite shape
Low melting and boiling point High melting and boiling point
Low polarity and more flammable High polarity and less flammable
Covalent bonds are in liquid or gaseous state at room temperature Ionic bonds have solid state at room temperature
Example: Methane, Hydrochloric acid Example: Sodium chloride, Potassium iodide

Question: Predict the formula of the ionic compound that forms from magnesium and oxygen?

Answer: We know, 

Electronic configuration of = 2, 8, 2

Electronic configuration of = 2, 6

Clearly, will lose 2 electrons and become where as will gain 2 electrons from 

and become which due to electrostatic forces of attraction will form (Magnesium oxide)

Frequently asked questions - FAQs

Question: Are ionic bonds formed between two non-metals?
Answer: Consider whether each element is a metal or a nonmetal to anticipate the sort of bond that will form between them. In general, nonmetals form covalent bonds, metals and nonmetals create ionic bonds, and metals and metals create metallic bonds.

Question: How do you break ionic bonds?
Answer: When ionic compounds are dissolved in water, they dissociate into ions through a process known as ionic dissociation or hydrolysis. After dissociation, it breaks apart into a negative and a positive ion and are hydrated by the polar water molecules as shown below. 


Question: What is isomorphism and polymorphism?
Answer: Isomorphism: When two or more crystals have similar chemical composition exist in the same crystalline form, this property is called isomorphism. 

e.g., and

Condition for isomorphism: 

1. Cations should have same electronic configuration
2. Anions should have same hybridization

e.g., and

Polymorphisms: When a particular substance exists in more than one crystalline form this property is called polymorphism.

e.g., Calcium carbonate exists in two crystalline formscalled calcite and aragonite

Related topics

Covalent bond Metallic bond
Chemical bonding Fajan's rule - Ionic character of covalent bond

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