Chemical Bond theory
The part of chemistry that studies from the theoretical point of view, the Chemical Bond and molecular structure, as well as issues related, it is called theory of chemical bonding and valence theory. The word valence is used to designate the ability of an element to be combined and also to indicate the number of chemical bonds that their atoms can form; thus, for example, an element is monovalent, divalent, trivalent, etc., if their atoms can form one, two, three, etc., chemical bonds, respectively. It is also common to say that an element can act with valence one, two, three, etc.
Overview of Lewis’ theory:
- N. Lewis and Irving Langmuir and Walther Kossel, made an important proposal above the chemical bond: electron configurations of noble gases atoms have something special, which is the cause of their chemical inertness and atoms of other elements combine with each other to acquire electronic configurations as those of noble gases atoms. The theory developed is called Lewis’ theory and its basic ideas are:
- Electrons, especially those in the outermost or valence layer, play a major role in the chemical bond.
- In some cases electrons from one atom are transferred to another, forming positive and negative ions attracted each other by electrostatic forces called ionic bonds.
- In other cases one or more pairs of electrons are shared between; this sharing of electrons is called covalent bond.
- Electrons are transferred or shared so that the atoms acquire a particularly stable electronic configuration. Generally, it is a noble gas configuration with eight outermost electrons which constituting an octet.
A Lewis’ symbol is a chemical symbol that represent the core and the inner electrons of an atom, with points which are located around the symbol representing the valence electrons, or outer electrons.
Lewis’ structure is a Lewis symbols combination that represent the transfer or the share of electrons in a chemical bond.
The chemical bond is generally quite complex, so to facilitate its study, it is usually divided into several types of links:
- Ionic bond
- Covalent bond
- Metallic bond
- Hydrogen bond
- Van der Waals forces
You can download the App BioProfe READER to practice this theory with self-corrected exercises.