Question

The strength of van der waal’s forces increases
\[\left( A \right)\] Increase in molecular size
\[\left( B \right)\] Increase in the number of electrons in the molecules
\[\left( C \right)\] Increase in molecular weight
\[\left( D \right)\] all of the above

Answer 1

Hint: when an atom joins together in a definite ratio to form a molecule. Different molecules have different shapes and properties. Different types of force of attraction occurs between the molecules.

Complete step by step answer:
- When molecules are formed and in molecule’s different types of attraction occur. This force of attraction between molecules totally depends on how much distance occurs between the molecules.
- This type of force of attraction also known as van der waals forces. This type of force arises due to fluctuation and nucleus shift one side and electron clouds shift another side. The nucleus side temporarily positive charge arises and electron clouds side arise negative charge so two poles are created one is positive pole and other is negative pole this is known as dipole. This dipole arises in non-polar molecules.
- When a dipole molecule and polar molecules come closer to each other than the positive pole of the dipole attracts negative charge of polar molecules. And the negative pole of dipole attracts towards the positive end of polar molecules. So this type of attraction is known as dipole-polar attraction.
- When this type of force of attraction occurs between two dipole molecules then this type of force of attraction is known as dipole-dipole attraction.
The strength of van der waal’s forces increases due to the increase in the number of electrons present and the size of the molecules. The correct answer is option “A and B” .

Note: Vander waal’s forces are very weak forces in nature as compared to ionic bond and covalent bond.
- These forces are totally independent of temperature.
- These forces occur when distance between molecules is very less.
- These forces are additive in nature.