A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction. From the small number of elements there are derived millions of known compounds, and there are an infinite number possible. This is because there are so many possible ways in which atoms combine to form molecules.
A chemical bond is defined as a force that acts between two or more atoms to hold them together as a stable molecule. Chemical bonding happens when atoms from two or more different elements combine to form a new substance. An atom is made of three different subatomic particles. Inside the nucleus, there are protons that have a positive charge and neutrons that have no charge. Circling the nucleus are electrons containing a negative charge. These electrons combine causing the elements to chemically bond.
The ability of two elements to form a chemical bond is based on valence electrons, or the electrons in the outermost shell. An atom looks much like a miniature version of a solar system, the atoms orbit around the nucleus much like a planet around the sun. Each orbit, or shell, can only hold a specific number of electrons. The first can only hold two, the second eight, the third eighteen and so forth. When an atom has it’s last shell filled, it is very stable and does not usually combine with another atom of a different element to go through a chemical bonding process. When that shell is empty, the atom isn’t as stable and attracts atoms of other elements to fill its shell and become stable
The beginning of our modern theory of bonding can be treated to the concept of valency introduced in 1850. The term valency has been derived from the Latin word ‘valentia’ which means capacity. Each element was said to have a valency equal to its combining capacity. The number of hydrogen or chlorine atoms with which another atom combines is called its combining capacity.
Thus, the concept of valency as mere number was very confusing. Later on, the definition of valency was changed. Valency was termed as the number of Chemical bonds formed by an atom in a molecule.
The modern concept of valency deals with the interactions between atoms in light of the structure of atoms, i.e., electronic configurations of atoms. The modern concept believes that electrons are responsible for chemical combination. It provides tools to find out the answer to the following questions:
(i) Why do atoms combine?
(ii) How do atoms combine together?
(iii) How can the properties of compounds be understood in terms of chemical bonds?
TYPES OF BONDS
1. Ionic Bonds
2. Covalent Bonds