Bonds
The atoms form molecules primarily due to the electrostatic interaction between the electrons and the nuclei. These interactions are described in terms of different kinds of bonds. We shall briefly discuss two important bonds that frequently occur in materials.
Ionic Bond
In an ionic bond two atoms come close to each other and an electron is completely transferred from one atom to the other. This leaves the first atom positively charge and the other one negatively charged. There is an electrostatic attraction between the ions which keeps them bound. For example, when a sodium atom comes close to a chlorine atom, an electron of the sodium atom is completely transferred to the chlorine atom. The positively charge sodium ion and the negatively charged chlorine ion attract each other to form an ionic bond resulting in sodium chloride molecule.
Covalent Bond
In many of the cases a complete transfer of electron from one atom to another does not take place to forma bond. Rather, electrons from neighbouring atoms are made available for sharing between the atoms. Such bonds are called covalent bond. When two hydrogen atoms come close to each other, both the electrons are available to both the nuclei. In other words, each electron moves through the total space occupied by the two atoms. Each electrons is pulled by both the nuclei. Chlorine molecule is also formed by this mechanism. Two chlorine atoms share a pair of electrons to form the bond. Another example of covalent bond is hydrogen chloride (HCL) Molecule.
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