- NaCl forms when sodium gives 1 electron to chlorine, making Na⁺ and Cl⁻ ions.
- MgCl₂ forms when magnesium gives 2 electrons, one to each chlorine atom.
- CaO forms when calcium gives 2 electrons to oxygen, forming Ca²⁺ and O²⁻.
- Electron dot structures show how electrons are transferred during ionic bonding.
- Ionic bond formation is a redox process—metals lose electrons (oxidation), non-metals gain (reduction).
Definitions [25]
Definition: 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.
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
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: Electronegative Element
A non-metallic element, whose atom readily accepts electron(s) to form a negatively charged ion, is an electronegative element.
Definition: Electropositive Element
A metallic element, whose one atom readily loses electron(s) to form a positively charged ion, is an electropositive element.
Definition: Anion
A non-metallic atom, which gains electron(s), becomes a negatively charged ion and is known as an anion.
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: 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: Electrovalency
The number of electrons that an atom of an element loses or gains to form a electrovalent bond is called its electrovalency.
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: 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.
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.
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.
Definition: Covalent Molecule
The molecule formed due to the sharing of electrons (covalent bond) is called a covalent molecule.
Definition: Covalency
The covalency of an atom is the number of its electrons taking part in the formation of shared pairs.
Definition: Polar Covalent Compounds
The covalent compounds are said to be polar when the shared pair of electrons are not at equal distance between the two atoms.
Definition: Non-Polar Covalent Compounds
Covalent compounds are non polar when shared pair of electron(s) are equally distributed between the two atoms.
Definition: Dipole Molecule
A molecule that has both, slight positive and slight negative charge is called a Dipole molecule.
Definition: Ionisation
In solution, the fractional charges of polar covalent compounds are converted to complete charges and ions are produced. The process by which covalent compounds are converted into ions is called ionisation.
Define
an electrovalent compound
Electrovalent compounds: The chemical compounds containing electrovalent bonds are called electrovalent or ionic compounds.
For example: Sodium chloride (NaCl).
Define
a covalent compound.
Covalent compounds: The chemical compound, formed as a result of mutual sharing of electrons or electron pairs thereby establishing a covalent bond is called a covalent or molecular compound.
For example: Hydrogen molecule (H2)
Definition: Lone Pair
A pair of electrons which is not shared with any other atom is known as the lone pair of electrons.
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.
Key Points
Key Points: Conditions for Formation of Electrovalent Bond
- Ionic bonds form when a metal with low ionisation energy transfers electrons to a non-metal with high electron affinity.
- A large electronegativity difference between the two atoms favours the formation of electrovalent bonds.
- Ionic compounds are stable due to strong electrostatic attraction between oppositely charged ions, despite repulsion between like charges.
Key Points: Structures of Some Electrovalent Compounds
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: Types of Covalent Bonds
- A single covalent bond involves sharing one pair of electrons; seen in H₂, Cl₂, CH₄, NH₃, and H₂O.
- Double bond shares two pairs of electrons (e.g., O₂, CO₂); triple bond shares three pairs (e.g., N₂, C₂H₂).
- Molecules like ethene (C₂H₄) and ethyne (C₂H₂) have combinations of single and double/triple bonds.
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.
Important Questions [24]
- Define a coordinate bond.
- State the type of bonding in the following molecule. Water
- Choose the Correct Answer Which of the Following is a Common Characteristic of a Covalent Compound?
- Non-polar covalent compounds are ______ conductors of heat and electricity.
- An Element L Consists of Molecules. What Type of Bonding is Present in the Particles that Make up L?
- Give Appropriate Scientific Reasons for Carbon Tetrachloride Does Not Conduct Electricity.
- Explain the Bonding in Methane Molecule Using Electron Dot Structure.
- Choose the most appropriate answer from the following list of oxides which fit the description. A covalent oxide of a metalloid.
- Name the Following: the Property of Element by Virtue of Which Atoms of the Element Can Link to Each Other in the Form of a Long Chain Or Ring Structure.
- The Covalent Bond in Which the Electrons Are Shared Equally Between the Combining Atoms.
- The general formula of hydrocarbons with single covalent bonds is ______.
- The following table shows the electronic configuration of the atoms A, B, C and D. Element A B C D Electronic configuration 2, 8, 8, 2 2, 6 2, 8, 7 2, 4 Write the formula of the compound
- Draw the electron dot structure for the following: A molecular nitrogen [At. No. : N = 7, H = 1]
- Draw the electron dot structure of Methane molecule. [Atomic number: N = 7, C = 6, H = 1]
- Draw the electron dot structure of Nitrogen molecule. [Atomic number: N = 7, C = 6, H = 1]
- Carbon tetrachloride is a ______ covalent molecule.
- Choose the Most Appropriate Answer of the Following: Bonding in this Molecule Can Be Understood to Involve Coordinate Bonding
- By Drawing an Electron Dot Diagram Show the Formation of Ammonium Ion Atomic No.: N = 7 and H = 1
- Identify the Term/Substance in the Following: the Electrons Present in the Outermost Shell of an Atom
- Give reason for the following: Covalent compounds have a low melting and boiling point.
- Choose the Correct Answer from the Options Given Below: a Compound X Consists of Only Molecules. Hence, X Will Have
- Give a reason for Inert gases do not form ions.
- The Following Table Shows the Test a Student Performed on Four Different Aqueous Solutions Which Are X, Y, Z and W. Based on the Observations Provided, Identify the Cation Present:
- Identify the Anion Present in the Following Compounds: a Salt M on Treatment with Concentrated Sulphuric Acid Produces a Gas Which Fumes in Moist Air and Gives Dense Fumes with Ammonia
Concepts [11]
- Concept of Chemical Bonding
- Ionic or Electrovalent Bond
- Conditions for the Formation of an Electrovalent (or ionic) Bond
- Structures of Some Electrovalent Compounds
- The Covalent Bond
- Types of Covalent Bonds
- Non-Polar and Polar Covalent Compounds
- Formation of Covalent Bond
- Properties and Comparison of Electrovalent and Covalent Compounds
- Effect of Electricity on Electrovalent and Covalent Compounds
- Coordinate Bond
