- An intramolecular force is the force that holds the atoms or ions together in a compound.
- There are 3 main types of intramolecular force:
- Metallic Bonding
- Ionic Bonding
- Covalent Bonding
- Intramolecular forces are much stronger than intermolecular forces (the forces that act between discrete molecules).
- The physical properties of metals and ionic substances are dependent ONLY on strong intramolecular forces (metallic bonding and ionic bonding)
- The physical properties of three dimensional covalent network substances are determined by strong intramolecular forces (covalent bonding)
- The physical properties of molecular covalent substances are determined by weaker intermolecular forces.
Comparison of Intramolecular Forces
||metal atoms bond to each other
||cations and anions bond
||2 atoms share a pair of electrons and each atom provides 1 electron for the bonding pair.
A coordinate covalent bond (dative bond) forms when 2 atoms share a pair of electrons but one of the atoms provides both electrons for the bonding pair
||metal and non-metal ions
||delocalised electrons shared between atoms
||cations and anions are held together by electrostatic attraction or forces
||electrons are shared between two atoms
||Group I (alkali) Metals, eg, Na
Group II (alkali earth) Metals, eg, Mg
Transition Metals, eg, Fe
|Group I Metal + Non-metal, eg, NaCl
Group II Metal + a non-metal, eg, MgCl2
Group VII elements, eg, Cl2,
Group VI non-metals, eg, O2
hydrogen + non-metal, eg, H2O
Coordinate covalent bond examples: NH4+, H3O+
Three dimensional covalent networks: Si, C (graphite and diamond), B, SiO2(quartz)
||Molecular Substances: low
Three dimensional covalent networks: high
|solubility in water
||Molecular Substances: dependent on the intermolecular forces
Three dimensional covalent network solids are insoluble.
|conductivity of solid
|conductivity of liquid
|conductivity of aqueous solution
||usually poor unless the substance reacts with water to form ions (eg, HCl reacts with water to form hydrogen ions and chloride ions)