medium difficulty8 min

Ionic Bonding

Ionic bonding is the chemical bonding formed by transfer of electrons from one atom to another, producing oppositely charged ions that attract each other strongly.

In one line: Fixed ions do not conduct; mobile ions conduct.

Practice This Concept

Understand it

In ionic bonding, a metal atom usually loses electron(s) to form a cation, and a non-metal atom gains electron(s) to form an anion. The strong electrostatic attraction between these ions forms an ionic compound. In solid state, ions are fixed in position, but in molten or aqueous state, ions become mobile and can conduct electricity.

Example

In sodium chloride, sodium loses one electron to form Na⁺ and chlorine gains one electron to form Cl^-. Oppositely charged ions attract to form an ionic lattice.

Rule to remember

Ionic bond: electron transfer followed by electrostatic attraction between cations and anions.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

Magnesium has two valence electrons and oxygen needs two electrons.

1Magnesium transfers two electrons to oxygen, forming Mg²⁺ and O²⁻.
2Their charges balance to give MgO.

Method you can reuse

1Identify metal and non-metal.
2Write electron loss and gain.
3Form cation and anion.
4Balance charges.
5State electrostatic attraction and relevant property.

Sketch it in your answer

Use an electron-transfer dot diagram showing Na losing one electron to Cl, followed by Na⁺ and Cl^- attraction in an ionic lattice.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why does solid sodium chloride not conduct electricity but molten sodium chloride does?

Think first, then show answer

Solid sodium chloride has ions, but they are fixed in the lattice and cannot move. In molten sodium chloride, ions are mobile, so they carry charge and conduct electricity.

Common wrong answer

Saying a solid ionic compound conducts because electrons move freely.

Why it loses marks: Ionic compounds conduct through mobile ions, not free metallic electrons.

Don't mix this up

Students often say solid ionic compounds conduct electricity because they contain ions. They conduct only when ions are mobile, such as in molten or aqueous state.

Exam tip

For properties, write strong electrostatic attraction for high melting point and mobile ions for conductivity in molten or aqueous state.

Ionic Bonding diagram

Open full screen to read every label clearly.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Asked through electron-transfer diagrams, conductivity of solid versus molten salt, high melting point, and formula formation from ion charges.

1
Enough for 1 mark
Ionic bonding is the chemical bonding formed by transfer of electrons from one atom to another, producing oppositely charged ions that attract each other strongly.
2
Add for 2 marks
Example: In sodium chloride, sodium loses one electron to form Na⁺ and chlorine gains one electron to form Cl^-. Oppositely charged ions attract to form an ionic lattice.
3
Add for 3 marks
In ionic bonding, a metal atom usually loses electron(s) to form a cation, and a non-metal atom gains electron(s) to form an anion.

MCQ Quiz

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