Ionic Bond (original) (raw)

Last Updated : 20 Apr, 2026

Atoms are the basic units of matter, but most atoms do not exist independently in nature. They combine with other atoms to form molecules and compounds. The force that holds atoms together in a molecule or compound is called a chemical bond. Chemical bonding occurs because atoms try to achieve a more stable electronic configuration, usually by completing their outermost shell (octet rule).

transfer_of_electrons

An ionic bond or electrovalent bond is a type of chemical bond formed when one atom completely transfers one or more electrons to another atom. This transfer of electrons usually happens between a metal and a non-metal.

**Example: Formation of NaCl

Properties of Ionic Bond

Ionic bonds are formed by the complete transfer of electrons, resulting in positively and negatively charged ions. Because of the strong electrostatic attraction between these ions, ionic compounds show the following properties:

**1. High Melting and Boiling Points

**Example: NaCl melts at about 801°C.

**2. Hard and Brittle Nature

**Example: Common salt (NaCl) crystals break easily when hit.

**3. Solubility in Water

**Example: NaCl dissolves in water.

**4. Electrical Conductivity

**Example: Molten NaCl conducts electricity.

**5. Formation of Crystalline Solids

**6. Strong Electrostatic Forces

**Example:
MgO has stronger ionic bond than NaCl (because Mg²⁺ and O²⁻ have higher charges).

Formation of Ionic Bond

The formation of an ionic bond depends on several important factors that make electron transfer possible and stable.

**1. Low Ionisation Energy

**Example:

Sodium (Na) easily loses one electron:
Na → Na⁺ + e⁻

Because Na has low ionisation energy, ionic bond formation becomes easier.

**2. High Electron Affinity

**Example:

Chlorine (Cl) gains one electron:
Cl + e⁻ → Cl⁻

Chlorine has high electron affinity, so it readily forms Cl⁻ ion.

**3. Large Difference in Electronegativity

**Example:

Na (low electronegativity), Cl (high electronegativity) → Forms ionic bond in NaCl.

**4. High Lattice Energy

**5. Stable Electronic Configuration (Octet Rule)

**Example:
Na (2,8,1) → becomes 2,8 after losing 1 electron.
Cl (2,8,7) → becomes 2,8,8 after gaining 1 electron.

Both become stable.

Preparation of Ionic Bond

An ionic bond is formed when one atom completely transfers one or more electrons to another atom. This usually happens between a metal and a non-metal.

The formation of an ionic bond takes place in three main steps:

**Step 1: Formation of Positive Ion (Cation)

The metal atom loses one or more electrons to become a positively charged ion.

Metals have:

**Step 2: Formation of Negative Ion (Anion)

The non-metal atom gains the electron lost by the metal and becomes negatively charged.

Non-metals have:

**Step 3: Formation of Ionic Bond

Now the oppositely charged ions attract each other due to strong electrostatic force. This attraction forms the ionic bond.

Formation of NaCl

In NaCl, sodium (Na), a metal, loses one electron to achieve a stable noble gas configuration, while chlorine (Cl), a non-metal, gains that electron to complete its octet. The resulting oppositely charged ions (Na⁺ and Cl⁻) are held together by strong electrostatic forces of attraction, forming a stable ionic lattice.

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**a) Electronic Configuration of Atoms

Both want to achieve stable noble gas configuration (octet).

**b) Loss of Electron by Sodium

Sodium easily loses one electron because it has low ionisation energy.

Na → Na⁺ + e⁻

Now sodium becomes stable like Neon.

**c) Gain of Electron by Chlorine

Chlorine needs one electron to complete its octet.

Cl + e⁻ → Cl⁻

Now chlorine becomes stable like Argon.

**d) Formation of Ionic Bond

Now Na⁺ and Cl⁻ are oppositely charged ions.

Na⁺ (+ charge)
Cl⁻ (– charge)

They attract each other due to strong electrostatic force.

Na⁺ + Cl - → NaCl

This attraction forms the ionic bond.

Examples of Ionic Bonds

There are various compounds which are formed by ionic bonds and these compounds are called ionic compounds. Various examples of the ionic bond are discussed in the table below,

Compound Cation Anion Reaction Electronic Configuration
NaCl Na+ Cl- Na → Na+ + e–Cl + e–→ Cl– Na = 2, 8, 1Cl = 2, 8, 7
CaCl2 Ca2+ 2Cl- Ca → Ca2+ + 2e–2Cl + 2e–→ 2Cl– Ca = 2, 8, 8, 2Cl = 2, 8, 7
CaO Ca2+ O2- Ca → Na2+ + 2e–O + 2e– → O2- Ca = 2, 8, 8, 2O = 2, 6

Ionic Bond vs Covalent Bond

Ionic Bond Covalent Bond
Ionic bonds are formed by the attraction of positive and negative ions in a crystal, and compounds held together by ionic bonds are known as ionic compounds. When two atoms share one or more electron pairs, they form a covalent bond. Each atom contributes an equal number of electrons to the formation of the bond.
In the formation of ionic bonds cations and anions are formed and held together by electrostatic attraction. No such intermediates are formed in the formation of covalent bonds.
Ionic bonds are formed between two atoms in which one atom is electronegative and the other is electropositive. As atoms with higher ionization potential do not lose their valence electrons easily, they prefer to form covalent bonds by sharing electrons.
If the electronegativity difference between the atom is very high they form ionic bonds. For instance, bonds formed in the KCl compound. If the electronegativities of the combining atoms are not significantly different, the bond formed between them is most likely covalent. For instance, bonds formed in the HCl compound
Examples of the compound with ionic bonds are,NaClCaCl2KOH, etc. Examples of the compound with covalent bonds are,H2ONH3CO2, etc.