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Ionic Compound

An ionic compound is a compound formed by attraction between oppositely charged ions.

In one line: Fixed ions cannot carry current; moving ions can.

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Understand it

Ionic compounds have strong electrostatic attraction between positive and negative ions, so they usually have high melting points. In the solid state, ions are fixed in place, so they do not conduct electricity. In molten or aqueous state, ions become mobile and can carry current.

Example

Sodium chloride is an ionic compound.

Rule to remember

Rule: ionic compounds conduct electricity only when ions are free to move, such as in molten or aqueous state.

See it worked out

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

Worked example

A dry salt crystal does not glow a bulb in a simple circuit, but melted salt can allow current to pass because the ions move through the liquid.

Method you can reuse

  1. 1Identify the state: solid, molten, or aqueous.
  2. 2In solid, ions are fixed.
  3. 3In molten or aqueous form, ions move.
  4. 4Conclude conductivity from ion mobility.

Visual tip

A lattice diagram with fixed ions in solid state and free ions in molten state is very useful here.

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 can conduct?

Think first, then show answer
In the solid state, the ions are fixed in the lattice, so they cannot move and carry charge. When sodium chloride is molten, the ions become mobile and can conduct electricity.

Common wrong answer

A common wrong answer is to say solid ionic compounds conduct because they contain charged particles, but charge alone is not enough without movement.

Don't mix this up

Students often think an ionic solid conducts electricity because it contains ions, but the ions must be mobile to carry current.

Exam tip

Check the state first: solid ionic compound usually does not conduct, but molten or aqueous ionic compound can conduct.

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

Questions often ask about conductivity in solid versus molten state, reasons for high melting point, or the role of ions in current flow.
  1. 1

    Enough for 1 mark

    An ionic compound is a compound formed by attraction between oppositely charged ions.

  2. 2

    Add for 2 marks

    Example: Sodium chloride is an ionic compound.

  3. 3

    Add for 3 marks

    Ionic compounds have strong electrostatic attraction between positive and negative ions, so they usually have high melting points.

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