Chemical Bonding and Molecular Structure
The smallest particle of element is atom and the smallest particle in a compound is molecule. The force or the binding that keeps the atoms in the molecule combined during the formation of molecule is called chemical bonding. The concepts like that of Kossel-Lewis, VSEPR principle, valence bond theory, molecular orbital theory have been presented. In chemical bonding, it has more relation with orbitals around the nucleus and especially the valence orbitals.
Chemical bonds form if the resulting arrangement of the atoms has lower energy than the separated atoms i.e., atoms combine to attain a state of lower energy (potential) than that in the isolated ones, e.g. H2, P4, S8, H2O, C6H12O6 etc. Various changes in energy that occur when bonds form results from the movement of the valence electrons (the electrons in the outermost shell) of atoms.
Ionic bond
It involves the complete transfer of one or more electrons from one atom to another and is characterized by a large difference in electronegativity. An ionic bond is formed between an electropositive and an electronegative element.
Covalent bond
It involves the sharing of a pair of electrons between two atoms and is characterized by a small difference in electronegativity. A covalent bond is formed between two electronegative elements or could be generated between a less electropositive and an
electronegative element.
Metallic bond
It involves the free movement of valence electrons throughout the crystal and is also characterized by small difference in electronegativity. A metallic bond is formed between two electropositive elements