INTERMOLECULAR FORCES

DEFINITION:are the forces of attraction between molecules or between atoms of noble gases.

IONISATION: the reaction of a molecule substance with water to produce ions.

  1. for example HCL is a covalent molecule that ionises in water.

  2. starts with H which will definitely ionise in water.

DISSOCIATION: the splitting of an ionic compound into its ions

  1. metal and non metals

  2. already made of ions so when you split them in water the ions separates.

  3. they become free moving in solution.( no new substance they just separate)

  4. the attraction of positive and negative ions pulls the ionic compounds apart that’s why it’s dissociation.

  5. 👉 Dissociation = ionic compound + water → ions separate

When you see dissociation:

👉 Split ions first

👉 Then fix charges

👉 Then balance numbers

ELECTROLYTE=a substance that can conduct electricity due to the presence of free ions when molten or dissolved in solution.

Examples of electrolytes

  • NaCl (molten or aqueous)

  • HCl (in water)

  • H₂SO₄ (in water)

  • KBr (in water)

TYPES OF INTERMOLECULAR FORCES

  • LONDON FORCES

  • weak force of attraction.

  • if it is non polar

  • simple covalent molecules(same atoms)

  • noble gases

🎯 FAST EXAM CHECK

1. Is it polar?

  • YES → not London-only

2. Does it have H–N/O/F?

  • YES → not London-only

3. If both NO → London only ✔

  • DIPOLE-DIPOLE

  • weak intermolecular force

  • between two molecules which are both polar(negative and positive ions)

  • shape is asymmetrical(different atoms or lone pairs; so bent shape, trigonal shape and pyramidal)

  • different electronegativity.

  • HYDROGEN BOND

  • strongest type of intermolecular forces

  • when there is N,O,F included.

  • that there is a lone pair in the molecule

  • high boiling point

  • high melting point

    Force type

    Strength

    Melting/boiling point

    Ionic bonds

    Very strong

    Very high

    Hydrogen bonding

    Strong

    High

    Dipole-Dipole

    Medium

    Moderate

    London forces

    Weak

    Low

EXTRA NOTES

Polar molecule

✔ Has polar bonds

✔ Shape is asymmetrical

✔ Different atoms

Non-polar molecule

✔ Has polar bonds shape is symmetrical( tetrahedral and linear)

✔ same atoms

Intramolecule= bonds between atoms inside a molecule