CHEMICAL BONDING AND ITS TYPES

 

Chemical bonding refers to the attraction between two atoms, this is a core phenomenon as it can promote the formation of new chemical substances, bonding can be between two or more atoms. The main reasons for chemical bonding is electrostatic force of attraction. Now, it should be kept in mind that this entire phenomenon is theoretical and not very practical as it can only be readily observed on a very sub-microscopic level in the lab.

One of the earliest attempt used to describe the chemical bonding was proposed in Lewis dot diagram. This diagram is still used today, a few examples of this are shown below-

                                            Image result for lewis dot diagram

Why do atoms combine?  

Atoms are less stable and more energetic hence, they form molecules to lose energy. Formation of bond is accompanied by decrease in potential energy. So, chemical bond formation is always exothermic. In a chemical bond, both attractive and repulsive forces exist in equilibrium. Also, a completely filled electronic configuration is highly stable. Hence, all other elements participate in chemical bond in order to acquire stable configuration.

Ways of combination –

Electronegative element + Electronegative element  → Covalent bond.        Electropositive element + Electronegative element → Ionic bond.

Ionic or Electrovalent bond - The strong electrostatic attraction between two oppositely charged ions which are formed due to transfer of electrons from one atom to another is called Ionic Bond (or) Electrovalent Bond. Formation of Ionic bond is a redox process because one atom undergoes oxidation other one undergoes reduction.

Ions are atoms or molecules which have either gained or lost one or more electrons thereby lending the ion a net positive or a net negative charge. There are two types of ions; Cations and Anions. Cations are ions carrying a net positive charge and anions are ions carrying a net negative charge.  Hence, the basic difference between a cation and an anion is the ion’s net electrical charge.     Cation Ion: Sodium: Na+, Hydronium: H3O+, and Ammonium: NH4                                                                                                                                               anion ion: Hydroxide Anion: OH–, oxide anion: O2-, and sulfate anion: SO42-

 

Covalent bonds- They  are formed when atoms share electrons (instead of gaining or losing them) to become more steady. When atoms share one, two or three pairs of electrons between themselves, it results in single, double or triple bonds respectively. The strength of the bond depends on the number of electrons that are shared between two atoms. More the number of electrons shared between two atoms, the stronger the bond between them. Covalent bonds are more commonly found in the molecules of all living organisms and also in smaller inorganic molecules like H2O, CO2, and O2. The structure of carbon-based organic molecules like our DNA and proteins also rely on Covalent bonds. The atom forms less number of covalent bonds in its ground state. The atom forms more number of covalent bonds in its excited state. Example:- Phosphorus atom has three unpaired electrons in its ground state. So, it can form only three covalent bonds in its ground state. Phosphorus atom has five unpaired electrons in its excited state. So, it can form five covalent bonds in its excited state.

Single bond is formed by the mutual sharing of one pair of electrons between two atoms.  Single bond is represented as '_____'

Double bond (Dicovalent bond) is formed by the mutual sharing of two pairs of electrons between two atoms.

Triple bond (Tricovalent bond) is formed by the mutual sharing of three pairs of electrons between two atoms. It is represented as ≡  Double and triple bonds are called multiple bonds.

Pure covalent bond is formed by the sharing of electron pairs between two like atoms. The word like atoms stands for atoms of the same element (or) atoms having same electro-negativity value. Pure covalent bond is present in H2, Cl2, O2, N2, P4, S8 etc.

Polar covalent bond is formed by the mutual sharing of electron pairs between two dissimilar atoms.The word dissimilar atoms stands for atoms of different elements (or) atoms having different electro - negativity values. In Polar Covalent bonding, the pair of electrons is not equally shared between two atoms. The reason for this is that one atom enjoys a stronger pull than the other atom and thereby attracts electrons. Hence, in Polar Covalent Bonds, one atom spends more time with electrons than the other atom resulting in an unequal sharing of electrons. Polar covalent bond is present in HF, HCl, ICl, H2O, CO2, SO2, BeCl2, SO3, BCl3, NH3, CH4, PCl5, SF6 etc.

 

Non-Covalent Bonds are formed when two atoms share a pair of electrons with each other. In Non-Covalent Bonds, two or more atoms are glued together to form a molecule by the shared electrons. Non-Polar Covalent Bonds are very strong bonds and a high amount of energy is required to break them. Non-Polar Covalent Bonds form the oxygen that we breathe and help make up our living cells.

Hydrogen bond – it is a weak electrostatic force between positively charged hydrogen atom of a polar molecule and a highly electronegative atom carrying negative charge. The highly electronegative atom may be present in the same molecule (or) in a different molecule. Represented by a dotted line (----) The length of the hydrogen bond varies from 1.76 A? to 2.75 A?and depends on the substance The energy of hydrogen bond varies from 2 to 10 K.cals/mole or 10-50 kJ / mole. It is weaker than covalent bond but stronger than Van der waals force of attraction.

Van der Waals forces- its a general term used to define the attraction of intermolecular forces between molecules. There are two kinds of Van der Waals forces: weak London Dispersion Forces and stronger dipole-dipole forces. London Dispersion Forces are weak bonds between molecules and can occur between atoms or molecules of any kind. These bonds are dependent on temporary imbalances in the distribution of electrons. Just like the Hydrogen Bonds, London Dispersion Bonds are weak attractions between molecules.

Chemical bonding is very important as it not only creates new chemicals but it also possesses the ability to change the properties of a substance, releasing or storing energy. Hence learning about the different types of chemical attractions and bondings connects us to the very basics of existence as everything we touch, breathe, see is formed by chemical bonds.

Hope this article helps you better your understanding about molecular bonds and structures.