How to do chemical bonding?
The fundamental questions in study chemistry ever since the beginning to study the nature of forces responsible for the construction of bond to form a molecule.
After nearly a century of confusion, Kekul, Van’t Hoff , Le Bel, Lewis, and London, etc in the nineteenth century given the concept of the construction of chemical bonds in chemistry.
It was easily realized that the number of atoms or groups of atoms combines to forming the ions or molecular species.
Every element has a saturation capacity for the construction of bonds and the valency commonly used for the saturation capacity of an element.
Definition of chemical bonding
Chemical bonding defines as the force holding together two atoms or groups of atoms forming an aggregate of ions or molecular species such that there occur lowering of energy.
Thus chemical bond represents the forces between atom or ions in a molecule. But there will be many chemical compounds whose properties would indicate intermediate types.
What are the different types of bonds?
To study different types of force holding together on atoms or ions for formation of molecule in our definition the chemical compounds form mainly three types of bonds.
- Ionic bond or electrovalent bond or electrostatic bond.
- Covalent bond.
- Metallic bond.
The ionic bond formed by electrostatic forces that bind together oppositely charged ions forms by the transfer of electron or electrons from an electropositive metal to an electronegative non-metal atom.
But the covalent bond defined as a force holding together atoms through the sharing of electrons.
Ionic bond definition and example
Ionic compounds constructed by the transference of electron or electrons from one atom to another.
Electropositive elements have a tendency to lose one or more electrons. But electronegative elements have a tendency to gain electrons.
Crystallographic studies show that there is no discrete sodium chloride molecule in the crystal of sodium chloride. Each sodium ion surrounded by six chlorine atom or vice versa.
Thus two oppositely charged ions held together by the electrostatic force of attraction.
Each sodium atom loses one electron to form uni positive sodium ion and neutral chlorine atom gains this electron to form uni negative ion.
The two ions constructed a close-packed type ionic sodium chloride crystal.
What type of elements form covalent bonds?
Covent bond formed by the sharing of electrons. Lewis represents the structure of the covalent bond of hydrogen and hydrogen fluoride.
A single covalent bond is formed between two hydrogen atom and hydrogen and a fluorine atom. Hence this type of bond formed by the sharing of only one electron between the bonded atom.
But a covalent double or triple bond formed by sharing two or three electrons between the atoms. And such type of bond formed in oxygen and nitrogen molecules.
The sharing of electrons equal to the partner not essential for the formation of a covalent bond sometimes.
For the formation of the compound boron trifluoride and ammonia both the electrons come from ammonia.
Hence such type of bond is called a coordinate covalent bond. Here ammonia as a donner and boron trifluoride is an acceptor.
How metallic bonds formed?
Metals are a good conductor of electricity and thermal energy. Metals formed crystalline solid with high coordination numbers of 12 or 14.
But all the atoms of metal, crystal are identical and they can not bound by an ionic bond. Two different types of atom formed this type of bond.
Covalent bonding also not possible for the formation of metallic crystals due to much weak van der Waals forces acting between covalent atoms.
Thus metallic crystal may be a collection of positive atomic cores immersed in a fluid of mobile electrons or sea of mobile electrons.
In the electron sea model, the force that binds a metal ion to the mobile electrons or sea of electrons known metallic bond.
The thermal and electrical conductivity of metals
This model can explain the conductivity and heat conduction in the metal.
Under the influence of the applied electric field, it is possible to move the electrons through the crystal lattice. Thereby metals are the conductor of electricity.
Heat conduction by the consequence of freedom of motion in electrons. Hence the higher energy transfers some energy to mobile electrons. Transfers these electrons one atomic core of the metal atom to another atomic core.
Thus most of the properties of the metal can explain by this type of bonding but the heat capacity of metals difficult to explain by these types of bonding.