Understanding Ionic Bonds | Chemistry for EmSAT Achieve PDF Download

• Chemical Bonding and Molecular Structure Class 11 Notes Chemistry Chapter 4
  • Chemical Bond: The force responsible for holding different atoms together in a molecule is termed as a chemical bond.
  • Octet Rule: Atoms of various elements engage in chemical bonding to achieve a complete octet or noble gas configuration.
  • Valence Electrons: These are the outermost shell electrons involved in chemical bonding.
  • Facts Stated by Kossel in Relation to Chemical Bonding:
    • In the periodic table, noble gases separate highly electronegative halogens and highly electropositive alkali metals.
    • Formation of anions and cations by halogens and alkali metals involves gaining and losing electrons, respectively.
    • Negative and positive ions attain noble gas configurations.
    • Electrostatic attraction stabilizes negative and positive ions.
  • Modes of Chemical Combination:
    • By the transfer of electrons: This results in an electrovalent or ionic bond where electrons are completely transferred between atoms.
    • By sharing of electrons: A covalent bond is formed through equal sharing of electrons between atoms.
    • Coordinate bond: Formed when one atom contributes electrons shared by both, known as a dative or coordinate bond.
  • Ionic or Electrovalent Bond:
    • Formed by complete electron transfer, usually between metals and non-metals, held together by electrostatic forces.
    • Compounds formed through ionic bonds are known as electrovalent compounds.
    • Example: NaCl is an electrovalent compound where Na+ gains configuration of Ne and Cl- represents the configuration of Ar.
  • Factors Affecting the Formation of Ionic Bond:
    • Ionization enthalpy: Lower ionization enthalpy facilitates cation formation, as seen in alkali metals.
    • Electron gain enthalpy: Higher electron gain enthalpy promotes anion formation, common in halogens.
    • Lattice energy: Influenced by ion size and charge, impacting the strength of the ionic bond.
  • General Characteristics of Ionic Compounds:
    • Physical state: Typically crystalline solids arranged in a crystal lattice structure.
    • Melting and boiling points: High due to strong interionic forces.
    • Solubility: Soluble in polar solvents but not in organic solvents.
    • Electrical conductivity: Poor in solid state but conductive in molten or aqueous states.
    • Ionic reactions: Rapid reactions with oppositely charged ions, forming new compounds.
  • Covalent Bond:
    • Lewis-Langmuir Concept: Formed through mutual electron sharing between atoms.
    • Lewis Representation of Simple Molecules: Utilizes steps to determine electron distribution in molecules.
    • Formal Charge: Charges assigned to individual atoms or ions in polyatomic ions.

Chemical Bonding Concepts

Chemical Bond

• A chemical bond is a force of attraction that holds atoms together in a compound.

Octet Rule

• The octet rule states that atoms tend to combine in such a way that they achieve a stable electron configuration with eight electrons in their outermost shell.

Valence Electrons

• Valence electrons are the electrons in the outermost shell of an atom that are involved in chemical bonding.

Facts About Chemical Bonding

• In chemical bonding, atoms share, donate, or receive electrons to achieve stability.

Ionic or Electrovalent Bond

• An ionic bond is formed between a metal and a non-metal through the transfer of electrons.

Lattice Energy of Ionic Compounds

• Lattice energy depends on factors such as the charge of ions and the distance between them.

Covalent Bond - Lewis-Langmuir Concept

• A covalent bond involves the sharing of electron pairs between atoms to achieve stability.

Lewis Structures

• Lewis structures represent how atoms are bonded together in a molecule using dots to symbolize electrons.

Formal Charge

• Formal charge helps determine the most stable arrangement of electrons in a molecule.

Limitations of the Octet Rule

• The octet rule has limitations in explaining the electron arrangement in some molecules.

Bond Length, Angle, Enthalpy, and Order

• Bond length is the average distance between the nuclei of two bonded atoms.
• Bond angle refers to the angle formed between bonded atoms.
• Bond enthalpy is the energy required to break a bond.
• Bond order indicates the number of chemical bonds between a pair of atoms.

Resonance Structures

• Resonance structures are different ways to represent a molecule using Lewis structures.

Polarity of Bonds and Dipole Moment

• Polar bonds have an uneven distribution of electron density.
• Dipole moment measures the polarity of a molecule.

Valence Shell Electron Pair Repulsion (VSEPR) Theory

• The VSEPR theory predicts the geometric shape of molecules based on electron pairs' repulsion.

Valence Bond Theory

• The valence bond theory explains how covalent bonds form through the overlap of atomic orbitals.

Hybridization

• Hybridization involves mixing atomic orbitals to form new hybrid orbitals.

Molecular Orbitals and Stability

• Molecular orbitals are formed by the overlap of atomic orbitals in a molecule.
• The stability of a molecule depends on its overall energy.

Bonding in Molecules and Hydrogen Bonding

• Some homonuclear molecules exhibit unique bonding properties.
• Hydrogen bonding occurs between hydrogen and highly electronegative elements like oxygen or nitrogen.