Intermolecular Forces and Metallic Bond Properties

Intermolecular Van der Waals Forces

Intermolecular Van der Waals forces are the forces that develop between the molecules of a covalent compound. These forces are far weaker than the chemical bonds themselves; they act by uniting various molecules, and their intensity depends mainly on the electronegativity difference between atoms forming the molecule and the size of the atoms. Consequently, the larger these factors are, the more intense the force between molecules will be.

Intermolecular forces are due to electrostatic attraction between permanent dipoles in heteronuclear molecules or induced dipoles in homonuclear molecules. The more intense the intermolecular forces, the greater the state of aggregation and the higher the melting and boiling points. In homonuclear molecules, the instantaneous deflection of the electron cloud is easier as the size of the atoms increases. In this sense, deformability increases, which explains the different aggregation states of the halogens.

Hydrogen Bonding

Hydrogen bonding occurs between molecules that have a hydrogen atom attached to a small and very electronegative atom. These forces are also electrostatic in nature, occurring between the hydrogen of one molecule (positive) and the negative part of neighboring molecules. They are more intense than Van der Waals forces and, therefore, are responsible for abnormal states of aggregation and higher melting and boiling temperatures.

Metallic Bonds

The metallic bond is found in all metallic elements. Metal bond formation is explained by assuming that each metal atom loses the electrons it has in excess of the noble gas configuration, converting into the corresponding metallic cation. These cations occupy all the knots in the metallic lattice. The electrons released by each atom form an electron cloud that surrounds the metallic network; thus, metallic bonding forces are responsible for the electrostatic attraction between metal cations and the electron cloud.

Properties of Metals

• 1) They are solid and very dense because their networks are very compact.
• 2) All metals possess a metallic brightness.
• 3) They are ductile and malleable.
• 4) They have high melting and boiling points due to the strength of the metallic link.
• 5) They conduct an electric current in a solid state because the electrons in the network are free to move.
• 6) They are insoluble in any solvent.