Question

Covalent-molecules are usually held in a crystal structure by-
A.Dipole-dipole attraction
B.Electrostatic attraction
C.Hydrogen bond
D.Van-der waals attraction

Answer 1

As we know that the intermolecular forces of attraction are mainly divided into four types and that is, Van der Waals dispersion forces, Van der Waals dipole – dipole interactions, hydrogen bonding, ionic bonds. And all have different appearances. In the case of hydrogen bond, it is an electrostatic force of attraction and it is present between hydrogen atoms which are bonded with a more electronegative group or atom. And the hydrogen bonds are mainly of two types, intermolecular H- bonding and intramolecular H- bonding.

Complete answer:
The covalent molecules are not held by Dipole-dipole attraction. Hence, option (A) is incorrect.
The covalent molecules are not held by Electrostatic attraction. Hence, option (B) is incorrect.
The covalent molecules are not held by Hydrogen bonds. Hence, option (C) is incorrect.
The covalent molecules are usually held in a crystal structure by Van-der Waals attraction. In the case of Van der Waals dipole – dipole interactions, it is a weak force of attraction which is present between the molecules having dipoles. A permanent dipole – dipole interaction is present between the polar molecules. And these polar molecules have one positive end and one negative end. And in Van der Waals dispersion forces, it is the weakest intermolecular forces of attraction and these are present between all the molecules with nonpolar molecules or polar molecules.

Note:
We have to know that the intermolecular forces are mainly four types. In that, the ionic bond is stronger than others due to the presence of static electrode attraction. And in the case of the hydrogen bond, it is the strongest bond, because it has only one electron. Therefore, there is a strong attraction between strong atoms and weak atoms. And a high amount of energy is required to break that bond.