Bonding and Structure

Bonding and Structure

1. Types of Bonds

   • Covalent Bonds
     • It is a shared pair of electrons
   • Ionic Bonds
     • It is the electrostatic attraction between oppositely charged ions
   • Metallic Bonds
     • It is electrostatic attraction between positive metal ions and delocalised electrons

2. Types of Structures

   • Giant Metallic Lattice
     • It is a 3D structure of positive ions and delocalised electrons bonded together by strong metallic bonds.
       • High melting point
         • Lots of energy is needed to break the strong metallic bonds between delocalised electrons and positive ions
       • Conduct electricity
         • The delocalised electrons are mobile i.e. free to move and carry current.
       • Malleable and Ductile
         • As the electrons in the metallic lattice are free to move, the structure has a degree to give, which allows layers of atoms to slide past each other.
   • Giant Ionic Lattice
     • It is a 3D structure of oppositely charged ions bonded together by strong ionic bonds
       • High Melting Point
         • Lots of energy is needed to break stonng electrostatic attraction between oppositely charged ions.
       • Electrical conductivity
         • Does not conduct when solid
           • Ions in solids have fixed position and hence are not mobile i.e. free to move
         • Conduct when molten or dissolved
           • The ions are mobile and free to move to carry current
       • Soluble in polar solvents
         • Water molecules attract Na+ and Cl- ions in ionic lattice. Na+ attracts δ- charges on oxygen atoms of the water molecule and Cl- attracts δ+ charges on hydrogen atoms of the water molecules. The ionic lattice breaks down as water molecules surround the ions and dissolve it.
   • Covalent Structures
     • Giant Covalent Structure
       • It is a 3D structure of atoms bonded together by strong covalent bonds.
         • High Melting Point
           • Lots of energy is needed to break the strong covalent bonds which are broken when melting gian colvalent lattice
         • Does not conduct electricity
           • There are no charged particles to carry current
         • Insoluble
           • The covalent bonds are too strong to be broken by wither polar or non-polar solvents
     • Simple molecule
       • It is a 3D structure of molecules bonded together by weak intermolecular forces.
         • Low Melting Point
           • Less energy is needed to break the weak intermolecular forces between molecules.
             • Three types of weak intermolecular forces
               • Van der Waals' Forces
                 • It is the weak attractive forces between induces dipoles of neighbouring molecules
               • Permanent DIpole-Dipole attraction
                 • It is the weak attractive forces between permanent dipoles of neighbouring molecules
               • Hydrogen bonding
                 • It is the strong dipole-dipole attraction between an electron-deficient hydrogen atom on one molecule and the lone pair of electrons on a highly electronegative atom on a different molecule. (O/N/F)
         • Do not conduct electricity
           • No charged particles free to move and carry current
         • Soluble in non-polar solvent
           • Weak Van Der Waal's forces arise between the non-polar covalent molecules and non-polar solvent molecules. this weakens the structure and causes it to break down.

3. COVALENT BOND > METALLIC BOND > INTERMOLECULAR FORCES

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