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. The strength of chemical bonds varies considerably; there are "strong bonds" such as covalent or ionic bonds and "weak bonds" such as dipole-dipole interactions, the London dispersion force and hydrogen bonding.
Introduction Sigma Bond
First see about bonding. The presence of 8 electrons in the furthest shell of their atoms is responsible for stability of the noble gases, so atoms of all elements tend to obtain 8 electrons in their furthest shell by distribution electrons with other atoms and this is the reason of their chemical combinations.
Out of all the noble gases helium has 1s2 while the rest of the elements have s2p6 electronic pattern in their furthest energy levels. Since the noble gas configuration is the most constant structure an atom having the s2p6 configuration in the valency shell will have smallest amount trend to enter into chemical combination. Most other elements tend to acquire similar structures by losing of electrons with other elements. This is the basic reason of chemical combination.
Union of two or more atoms involving move or sharing of electrons between themselves so that all of them get the steady noble gas configuration is called as chemical bonding. The bonding is ionic if the union is by the transfer of electrons from one atom to the other and covalent if the union is recognized by the mutual sharing of electrons between the atoms. Now see about sigma bond.
Sigma bond is in the formation of ethane molecule, one of the hybridized bonds of each carbon atom is used up in giving C-C bond and the remaining three bonds of each carbon atom are linked with hydrogen atoms. That means, each bond in the ethane is formed by the overlapping of orbitals along their axes. Such bonds are known as the sigma bonds. A single bond produced between two atoms by overlapping of orbitals beside their axes is called as a sigma bond. Thus, all the C-C and C-H bonds in ethane are the sigma bonds.
In 1916, an American chemist NEWTON LEWIS proposed that chemical bonds are formed between atoms due to the interaction of electrons between them. A Chemical Bond is a term used when two or more atoms combine to form a stable compound or molecule. The reason why atoms or elements combine lies in their electronic shell configurations. Because in a chemical bond the valance shell of one atom will have less electron and the other will have more or equal, hence they will combine together to either share or donate the electrons to each other making a complete stable electronic configuration.
For example, when a Li atom and F atom combine then, Li can achieve a complete configuration by donating an electron to Fluorine, which also achieves complete electronic configuration as shown;
Newton Lewis observed that many elements are most stable when they have complete valence shells (eight electrons). Then he came to know that atoms having less than 8 electrons in their valance shell bond together to share electrons and complete their shells. While some of the Lewis predictions prove incorrect and there are compounds which have more than 8 electrons in their valance shell and are stable. These compounds fall in the categories of exceptional compounds.
There are two types of bonding present: 1. Ionic and 2. Covalent
Ionic bond: In Ionic Bond, electrons are completely transferred from one atom to another so that the atoms achieve stable electronic configuration. In this process, formation of ions takes place .The positive charged ions get attracted to negative charged ions, which forms the basis of an IONIC BOND. For example, in the reaction of Sodium (Metal) with Chlorine (Non metal),
Ionic compounds are generally solids, results from intermolecular forces between them .The chemical bond formed between Ionic compounds are the strongest of all. Ionic bonds dissolve very easily in water and other polar solvents. Ionic bonds conduct electricity and they have very high melting and boiling points.
Covalent bond: Covalent bonds are formed between the atoms where sharing of electrons takes place. It is opposite to Ionic bonds. Covalent bonds mostly occur between Non-Metals. A good example of a covalent bond is the bond formed between two Hydrogen atoms. Covalent bonds have no charges and no ions in their compounds. These bonds are weaker in comparison to Ionic.
The Chemical Bonds are basically the result of the electrical forces of attraction acting between the atoms, resulting in the formation of molecules. Different types of Chemical Bonds present in the compounds have varying intensity which is directly responsible for the physical and chemical properties of molecules and compounds like hardness , melting , boiling , conductivity , solubility , etc.
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