Introduction

Have you ever wondered how the world around us remains intact? From your kitchen salt, metal for your car, and even proteins inside your body- all of them are chemically bonded. It is this invisible force that gives rise to molecules, define materials, and provides the means for life.

However, all bonds are not the same. Chemistry talks of them mainly as being Ionic, Covalent, Coordinate Covalent Bond, and Metallic bonds. Each type plays a unique role in the structure and properties of substances.
Let us get into the science of bonds and the way matter is held together!

Chemical Bond

Chemical bonds are forces of interaction among atoms that enable them to bond and create stable forms. Atoms create chemical bonds when they share, transfer, or accumulate electrons to acquire a complete outer electron shell, which stabilizes them.

Cause of Chemical Combination or Bonding

The cause of Chemical Combination is the tendency of atoms of various elements to acquire stable configuration of the nearest noble gas.

Classification of Chemical Bonds

All the bonds are not same. In Chemistry, the chemical bonds are classified as:

• Ionic Bond
• Covalent Bond
• Coordinate Covalent Bond
• Metallic Bond

Electrovalent or Ionic Bond-The Complete transfer of electron

Ionic bond holds two atoms together due to the complete transfer of one or more valence electrons from one atom to the other.

This occurs when an element with low ionization energy (metals) react with nonmetals with comparatively high ionization energies. The transfer of electrons creates positively charged ions (cations) and negatively charged ions (anions) which are stabilized or held together due to electrostatic forces of attraction. Due to its Electrostatic nature of bonding forces, it is quite naturally called the Electrovalent Bond.

Example: In the formation of NaCl molecule, the Na atom has one electron in its outermost shell and requires seven more electrons to achieve a stable electronic configuration; therefore, it donates its electron to Cl, which has seven electrons in its valence shell and needs just one to reach a stable configuration. This process results in the formation of sodium chloride, or table salt (NaCl).

Sodium now becomes a positively charged ion (Na⁺), while Cl becomes a negatively charged ion (Cl⁻), and they stick together.

No Bond in Chemistry is 100% Ionic

A bond is said to be 100% ionic when one of the bonding atoms steals the bonding electrons. No bond in chemistry has 100% ionic character because there will always be some degree of electron sharing among the bonds. In chemistry, no bond necessarily has 100% ionic character, because the only coexisting part constitutes shared electrons. The atoms together can only share some degree of electron density.

Properties of Ionic compounds

• Exist as crystalline solids at room temperature.
• Very high melting and boiling points because of the strong electrostatic force of attraction.
• Soluble in polar solvents like water.
• Conduct electricity in the dissolved state or molten state due to the presence of free electrons.
• Very brittle (breaks under force due to repulsion between like charges).
• Very high density.
• Non directional character due to strong electrostatic forces of attraction.
• Show isomorphism such as NaF and MgO.

Covalent Bond or Electron Pair Bond-The Sharing of Electrons

According to Lewis and Kossel, Covalent Bond is formed by the mutual sharing of electrons between combining atoms of same or different elements.

According to Orbital concept, Covalent Bond is formed between two atoms when a half filled valance orbital of one atom overlaps with a half filled valance orbital of the other atom.

Example: Water (H₂O) is a perfect example. Each hydrogen atom shares its single electron with oxygen, which shares two of its electrons in return. This sharing creates a strong bond and gives water its unique properties, such as high surface tension and the ability to dissolve many substances.

Types of Covalent Bond

Depending upon the number of electrons shared, the covalent bond has the following types:

1. On the Basis of the Number of Shared Electron Pair

Single Covalent Bond

• It is a covalent bond formed by mutual sharing of one electron pair between the participating atoms.
• For example, Hydrogen molecule is composed of two hydrogen atoms, each of which have one electron in it’s valance orbital which overlaps to give stable hydrogen molecule.
• A single covalent bond is represented by a single line drawn between the combining atoms.

Double Covalent Bond

• It is a covalent bond formed by the mutual sharing of two electron pairs between participating atoms.
• For example, Carbon dioxide and Ethylene C2H4.
• Double Covalent Bond is represented by a double line Drawn between combining atoms.

Triple Covalent Bond

• It is formed by the mutual sharing of three electron pairs between the participating atoms.
• Triple covalent bond is represented by three lines Drawn between combining atoms.
• For example, ethyne and nitrogen molecules.

2. On the Basis of Electronegativity Difference

Non-Polar Covalent Bond

• It is formed between the two similar or dis-smilar atoms of same electronegativity which attract the shared pair of electrons equally.
• For example, the bond formed between two hydrogen atoms.

Polar Covalent Bond

• It is formed between two dis-similar atoms of with moderate electronegativity difference due to which the shared pair of electrons is not equally shared between the participating atoms and is attracted more toward the atom with high electronegativity value.
• For example, the bond formed between hydrogen and chlorine atoms to form HCl.

Properties of Covalent Compounds

• Exist as gases , liquids or soft solids under normal conditions of temperature and pressure.
• Low melting and boiling points except giant molecules (e g., diamond, SiC etc)
• Bad conductors of electricity.
• Insoluble in polar solvents but some compounds like alcohols , amines etc are soluble in water due to hydrogen bonding.
• No brittleness
• Directional in character.
• Low density .
• Show isomorphism

Coordinate Covalent Bond or Dative Bond

It is a kind of two-center, two-electron covalent bond which is formed between the two atoms when the shared pair of electrons is donated by one of the bonded atoms.

• The atom which donates the electron pair is called Donor or ligand which is Lewis base.
• The atom which accepts the electron pair is called acceptor which is Lewis acid.
• For example, the bond formed between boron trifluoride and ammonia.
• Formation of Aluminum Chloride Al2Cl6
• The coordinate covalent bond is represented by an arrow which points away from the donor to the acceptor.
• The process of formation of this bond is called coordination.

Properties of Coordinate Covalent Compounds

• Solids, liquids or gases.
• Melting and boiling points are higher than covalent compounds but lower than ionic compounds.
• Don’t conduct electricity.
• Soluble in non polar solvents.
• Rigid and directional in character.
• Show isomorphism.
• Low density.

Metallic Bond-The Sea of Electrons

In these bonds, atoms release their outer electrons into a shared “sea”, creating a lattice of positively charged ions surrounded by freely moving electrons.

Metallic bonds occur in metals, where atoms share a sea of delocalized electrons. These electrons move freely through the structure giving metals their unique properties.

Example: In a piece of copper (Cu), the outer electrons of copper atoms are shared among all the atoms in the metal.

Properties of Metals

• Solids at room temperature except mercury which is liquid at room temperature.
• High melting and boiling points
• Malleability (can be drawn into thin sheets)
• Ductility (can be drawn into wires)
• High electrical and thermal conductivity.
• Show metallic luster.
• High density.

Conclusion

Chemical bonds are the unseen forces behind the binding of the universe, from ordinary objects to the building blocks of life. The properties and disposition of any matter are therefore dictated by ionic, covalent, coordinate covalent, and metallic bonds. Their roles range from the conductivity of metals to the solubility of salts. Understanding these bonds unravels chemistry and opens doors to discoveries. Ultimately, chemical bonds render stability, structure, and life possible.

Read More: Accuracy, Precision, Specificity and Sensitivity in Chemical Analysis

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The post How Atoms Stick Together: The Science Of Chemical Bonds appeared first on IM Group Of Researchers - An International Research Organization.