- Combustion fully oxidises carbon compounds, breaking all chemical bonds and producing CO₂ and H₂O.
- Oxidising agents like potassium permanganate or potassium dichromate can convert alcohols to carboxylic acids.
- Air inlets in stoves ensure complete combustion; black soot indicates incomplete combustion and fuel wastage due to blocked air inlets.
Definitions [33]
In term of electron transfer, define
Reduction
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.
Definition: Chemical Bond
A chemical bond may be defined as the force of attraction between any two atoms in a molecule to maintain stability.
or
The phenomenon of union of two or more atoms by redistribution of electrons, so that each atom involved in bonding acquires stable configuration to gain stability or to achieve a state of lower energy is called chemical bonding.
Define a chemical bond.
A chemical bond may be defined as the force of attraction between any two atoms, in a molecule, to maintain stability.
In term of electron transfer, define Oxidation
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.
Definition: Electrovalent (or Ionic) Compounds
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.
Definition: Anion
A non-metallic atom, which gains electron(s), becomes a negatively charged ion and is known as an anion.
Definition: Electropositive Element
A metallic element, whose one atom readily loses electron(s) to form a positively charged ion, is an electropositive element.
Definition: Electronegative Element
A non-metallic element, whose atom readily accepts electron(s) to form a negatively charged ion, is an electronegative element.
Definition: Electrovalent Bond
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.
Definition: Ion
An ion is a charged particle which is formed due to the gain or the loss of one or more electrons by an atom.
Definition: Cation
A metallic atom, which loses electron(s), becomes a positively charged ion and is known as a cation.
Definition: Electrovalency
The number of electrons that an atom of an element loses or gains to form a electrovalent bond is called its electrovalency.
Definition: Electrovalent Bond
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.
Definition: Electrovalent (or Ionic) Compounds
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.
Definition: Cation
A metallic atom, which loses electron(s), becomes a positively charged ion and is known as a cation.
Definition: Ion
An ion is a charged particle which is formed due to the gain or the loss of one or more electrons by an atom.
Definition: Anion
A non-metallic atom, which gains electron(s), becomes a negatively charged ion and is known as an anion.
Definition: Electrovalency
The number of electrons that an atom of an element loses or gains to form a electrovalent bond is called its electrovalency.
Definition: Electropositive Element
A metallic element, whose one atom readily loses electron(s) to form a positively charged ion, is an electropositive element.
Definition: Electronegative Element
A non-metallic element, whose atom readily accepts electron(s) to form a negatively charged ion, is an electronegative element.
Define a coordinate bond.
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.
Define a covalent bond.
The chemical bond formed between two combining atoms by mutual sharing of one or more pairs of electrons is called a covalent bond.
Definition: Covalent Compound
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.
Definition: Covalent Molecule
The molecule formed due to the sharing of electrons (covalent bond) is called a covalent molecule.
Definition: Coordinate Bond
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 or dative bond.
Definition: Lone Pair
A pair of electrons which is not shared with any other atom is known as the lone pair of electrons.
Define reduction.
Those reactions in which hydrogen combines with a substance or oxygen is removed from a substance, are known as reduction reactions.
Example: \[\ce{2HgO->[heat]2Hg +O2}\]
Define corrosion.
When the surface of a metal is attacked by air, moisture or any other substance around it, the metal is said to corrode and the phenomenon is known as corrosion.
Corrosion is an electrochemical process in which a metal is oxidised to a metal oxide or another salt of the metal by losing electrons to oxygen or another electronegative element, forming a coating on the metal surface.
Define an oxidation reaction.
The chemical reaction in which reactants gain oxygen to form the corresponding oxide. Also, A chemical reaction in which reactants lose hydrogen to form a product is called oxidation.
Example: \[\ce{H2S + Cl -> 2HCl + S}\]
Define oxidation number.
The oxidation number of an element is defined as the formal charge that an atom of that element appears to have when electrons are counted.
Definition: Oxidants or Oxidising Agents
Chemical substances which bring about an oxidation reaction by making oxygen available are called oxidants or oxidizing agents.
OR
Substances that can give oxygen to other substances are called oxidants or oxidizing agents.
Define redox reaction.
Redox reactions are those in which reduction and oxidation both takes place simultaneously i.e. one substance is reduced while the other gets oxidised.
Definition: Oxidation Reaction
The chemical reaction in which a reactant combines with oxygen or loses hydrogen to form the product is called oxidation reaction.
Key Points
Key Points: Ionic (Electrovalent) Bond
An ionic bond is formed by the complete transfer of one or more electrons from an electropositive atom to an electronegative atom, resulting in oppositely charged ions that attract each other.
Key conditions for ionic bond formation:
-
One atom must have low ionisation enthalpy (easily loses electron) — typically a metal
-
The other must have high electron affinity (easily gains electron) — typically a non-metal
-
Large difference in electronegativity between the two atoms
Example: Na + Cl → Na⁺ + Cl⁻ → NaCl
-
Sodium (2,8,1) loses 1 electron → Na⁺ (2,8)
-
Chlorine (2,8,7) gains 1 electron → Cl⁻ (2,8,8)
Ionic solids are crystalline structures containing cations and anions held together by strong electrostatic ionic bonds.
Key Points: Ionic (Electrovalent) Bond
An ionic bond is formed by the complete transfer of one or more electrons from an electropositive atom to an electronegative atom, resulting in oppositely charged ions that attract each other.
Key conditions for ionic bond formation:
-
One atom must have low ionisation enthalpy (easily loses electron) — typically a metal
-
The other must have high electron affinity (easily gains electron) — typically a non-metal
-
Large difference in electronegativity between the two atoms
Example: Na + Cl → Na⁺ + Cl⁻ → NaCl
-
Sodium (2,8,1) loses 1 electron → Na⁺ (2,8)
-
Chlorine (2,8,7) gains 1 electron → Cl⁻ (2,8,8)
Ionic solids are crystalline structures containing cations and anions held together by strong electrostatic ionic bonds.
Key Points: The Covalent Bond
- 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.
Key Points: Formation of Covalent Bond
- Atoms involved in covalent bonding must be non‑metals.
- High electronegativity in both atoms favors covalent bond formation.
- High electron affinity in both atoms helps them attract shared electrons.
- High ionization energy makes atoms less likely to lose electrons, supporting electron sharing instead.
- The electronegativity difference between the two atoms should be zero or very small for a covalent bond to form.
Key Points: Oxidation
