Revision: Chemical Bonding and Molecular Structure JEE Main Chemical Bonding and Molecular Structure

Oxidation is the loss of electrons during a reaction by a molecule, atom or ion. In terms of electron transfer, oxidation is defined as the phenomenon in which an atom loses an electron to form a positively charged cation.
During the formation of ionic bond one atom undergoes oxidation while another atom undergoes reduction.

A chemical bond may be defined as the force of attraction between any two atoms, in a molecule, to maintain stability.

Reduction is defined as the phenomenon in which an atom gains an electron to form a negatively charged ion called an anion.
During the formation of ionic bond one atom undergoes oxidation while another atom undergoes reduction.

A chemical bond may be defined as the force of attraction between any two atoms in a molecule to maintain stability.

Octet rule: Atoms of elements combine with each other in order to complete their respective octets so as to acquire the stable gas configuration.

The octet rule or the electronic theory of chemical bonding was developed by Kossel and Lewis. According to this rule, atoms can combine either by transfer of valence electrons from one atom to another or by sharing their valence electrons in order to attain the nearest noble gas configuration by having an octet in their valence shell.

The octet rule successfully explained the formation of chemical bonds depending upon the nature of the element.

The number of electrons that an atom of an element loses or gains to form a electrovalent bond is called its electrovalency.

The chemical compounds formed as a result of the transfer of electrons from one atom of an element to one atom of another element are called ionic (or electrovalent) compounds.

The cation and the anion being oppositely charged attract each other and form a chemical bond. Since this chemical bond formation is due to the electrostatic force of attraction between a cation and an anion, it is called an electrovalent (or an ionic) bond.

A non-metallic element, whose atom readily accepts electron(s) to form a negatively charged ion, is an electronegative element.

A metallic element, whose one atom readily loses electron(s) to form a positively charged ion, is an electropositive element.

A non-metallic atom, which gains electron(s), becomes a negatively charged ion and is known as an anion.

A metallic atom, which loses electron(s), becomes a positively charged ion and is known as a cation.

An ion is a charged particle which is formed due to the gain or the loss of one or more electrons by an atom.

The number of bonds formed between the two bonded atoms in a molecule is called the bond order.

Bond order = `("N"_"b" - "N"_"a")/2`

The bond enthalpy is defined as the minimum amount of energy required to break one mole of a particular bond in molecules in their gaseous state. The unit of bond enthalpy is kJ mol^-1.

Bond length is defined as the equilibrium distance between the nuclei of two bonded atoms in a molecule.

Bond lengths are expressed in terms of Angstrom (10^–10 m) or picometer

(10^–12 m) and are measured by spectroscopic X-ray diffractions and electron-diffraction techniques.

In an ionic compound, the bond length is the sum of the ionic radii of the constituting atoms (d = r₊ + r_–). In a covalent compound, it is the sum of their covalent radii (d = r_A+ r_B).

Bond-length: It is the equilibrium distance between the nuclei of two bonded atoms in a molecule. Bond-lengths are measured by spectroscopic methods

Electronegativity is the ability of an atom in a chemical compound to attract a bond pair of electrons towards itself.

Electronegativity of any given element is not constant. It varies according to the element to which it is bound. It is not a measurable quantity. It is only a relative number

Electronegativity is the tendency of an atom to attract shared pair of electrons. It is the property of bonded atom.

Hybridisation is the process of mixing of atomic orbitals of the same atom with comparable energy to form an equal number of new equivalent orbitals with the same energy.

The tendency of an atom in a molecule to attract the shared pair of electrons towards itself is called its electronegativity.

The chemical bond that is formed between two combining atoms by mutual sharing of one or more pairs of electrons is called a covalent (or a molecular) bond, and the compound formed due to this bond is called a covalent compound.

The molecule formed due to the sharing of electrons (covalent bond) is called a covalent molecule.

The bond formed between two atoms by sharing a pair of electrons, provided entirely by one of the combining atoms but shared by both, is called a coordinate bond. 

The chemical bond formed between two combining atoms by mutual sharing of one or more pairs of electrons is called a covalent bond.

• Electronegativity is the ability of an atom to pull shared electrons; it is highest for fluorine (4.0).
• It increases across a period (left to right) and decreases down a group (top to bottom).
• Non-metals have high electronegativity (gain electrons), while metals have low electronegativity (lose electrons).

• Carbon forms covalent bonds by sharing electrons to achieve a noble gas configuration.
• Covalent bonds can be single, double, or triple, as seen in molecules like H₂, O₂, and N₂.
• Covalent compounds have low melting and boiling points and are poor conductors of electricity.
• Carbon has allotropes such as diamond, graphite, and fullerene (C₆₀), each with different physical properties.