Intramolecular Forces |
Key Concepts
- 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
|
Metallic Bonding |
Ionic Bonding |
Covalent Bonding |
|---|
| occurs when |
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 |
|---|
| occurs between |
metal atoms |
metal and non-metal ions |
non-metal atoms |
|---|
| bond characteristics |
delocalised electrons shared between atoms |
cations and anions are held together by electrostatic attraction or forces |
electrons are shared between two atoms |
|---|
| typical example |
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 |
Molecular Substances:
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) |
|---|
| melting/boiling point |
high |
high |
Molecular Substances: low
Three dimensional covalent networks: high |
|---|
| solubility in water |
insoluble |
soluble |
Molecular Substances: dependent on the intermolecular forces
Three dimensional covalent network solids are insoluble. |
|---|
| conductivity of solid |
good |
poor |
usually poor |
|---|
| conductivity of liquid |
good |
good |
usually poor |
|---|
| conductivity of aqueous solution |
N/A |
good |
usually poor unless the substance reacts with water to form ions (eg, HCl reacts with water to form hydrogen ions and chloride ions) |
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Related AUS-e-TUTE Topics |
| Metallic Bonding
Ionic Bonding
Covalent Bonding
Intermolecular Forces
Naming Ionic Compounds
Writing Ionic Formula
Shapes of Molecules
Electronegativity and Bond Polarity
Molecule Polarity
Lewis Structures
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