Chem chap 2

• CHAPTER 2 - Chemical Bonding
• SYLLABUS - SCOPE OF SYLLABUS - in and after MARCH 2025-CHEMICAL BONDING - ELECTROVALENT. COVALENT & CO-ORDINATE BONDING, STRUCTURES OF VARIOUS COMPOUNDS, ELECTRON DOT STRUCTURE.
• Electrovalent bonding

  Electron transfer from a metallic atom to a non-metallic atom
• Electrovalent compounds

  • NaCl
  • MgCl2
  • CaO
• Characteristic properties of electrovalent compounds

  • State of existence
  • Melting & boiling points
  • Conductivity (heat & electricity)
  • Dissociation in solution & in molten state to be linked with electrolysis
• Covalent Bonding

  Sharing of valence electrons between atoms
• Polar Covalent compounds

  Based on difference in electronegativity
• Polar Covalent compounds

  • HCl
  • H2O
• Characteristic properties of Covalent compounds

  • State of existence
  • Melting & boiling points
  • Conductivity (heat & electricity)
  • Ionisation in solution
• Comparison of Electrovalent & Covalent compounds
• Coordinate Bonding


  Bonding involving a lone pair of electrons
• Lone pair effect


  Explains the formation of H3O+ & NH4+ ions
• Chemical bond is the force which holds two or more atoms together in a stable molecule
• Atom


  Smallest unit of matter taking part in a chemical reaction, built up of protons, neutrons and electrons
• Two or more atoms (metallic or non-metallic) combine to form a molecule
• Sub-atomic particles


  • Proton
  • Neutron
  • Electron
• Elements


  Pure substances made up of one kind of atoms - having the same atomic number
• Types of elements involved in chemical combination

  • Metallic elements (1, 2 or 3 valence electrons)
  • Non-metallic elements (4, 5, 6 or 7 valence electrons)
• Chemical combination


  • Transfer of valence electrons from a metallic atom to a non-metallic atom
  • Sharing of valence electrons between two atoms (generally both non-metallic)
• Noble gases have stable electronic configuration with complete valence shells
• Atoms of elements other than noble gases have unstable electronic configuration and are chemically reactive
• Reasons for chemical bonding

  Tendency of atoms to attain stable electronic configuration of the nearest noble gas
• Methods for achieving chemical bonding

  • Electron transfer (leading to electrovalent bonding)
  • Electron sharing (leading to covalent bonding)
• Periodic properties affecting ionic compound formation

  • Lower ionisation potential of metallic atom
  • Higher electron affinity of non-metallic atom
  • Larger electronegativity difference between combining atoms
• Periodic properties affecting covalent compound formation

  • High ionisation potential, electron affinity & electronegativity between both atoms
  • Negligible electronegativity difference between combining atoms
• Electrovalent bonding

  Bonding formed by transfer of valence electrons from a metallic atom to a non-metallic atom
• Electrovalent compound


  Compound formed by transfer of valence electrons from a metallic atom to a non-metallic atom
• Electrovalency


  Number of electrons donated or accepted by an atom to achieve stable electronic configuration
• Oxidation


  Process where an atom or ion loses electrons
• Reduction

  Process where an atom or ion gains electrons
• Oxidation-Reduction (Redox) reactions involve both oxidation and reduction
• Ions

  Electrically charged particles (cations and anions) that exist independently in solution
• Electrovalent or ionic bond is formed by electrostatic attraction between oppositely charged ions
• Formation of sodium chloride

  1. Sodium atom loses one electron

  2. Chlorine atom gains one electron

  3. Oppositely charged sodium and chloride ions attract to form ionic bond
• Electron dot structure represents the formation of ionic compounds
• Formation of calcium oxide

  1. Calcium atom loses two electrons

  2. Oxygen atom gains two electrons

  3. Oppositely charged calcium and oxide ions attract to form ionic bond
• Calcium oxide

  Formed as a result of transfer of two valence electrons
• Calcium atom


  • Attains stable electronic configuration of the nearest noble gas Argon by losing two electrons from its valence shell and becomes a positively charged calcium ion (cation) - Ca2+
  • Oxygen atom attains stable electronic configuration of the nearest noble gas Neon by accepting two electrons in its valence shell and becomes a negatively charged oxide ion (anion) - O2-
• Formation of calcium oxide

  Two oppositely charged ions (Ca2+ and O2-) attract each other resulting in formation of the electrovalent compound calcium oxide with an ionic bond
• Electron dot structure representation of formation of calcium oxide