Introduction
Octet Rule: Elements below period 2=can have expanded octet (have more than 4 electron orbitals avail
for bonding)
Intramolecular forces: Metallic bond included
Intermolecular forces: Hold secondary structures and give properties
Ionic Bonding
Nucleon properties:
- Protons repel e other, and neutrons would float away too
- Strong nuclear force holds together nucleus (quarks bringing p together)
EN differences (note that this is a continuum)
- 0=non-polar covalent(diatomic)
- <0.4=slightly polar covalent
- 0.4-1.7=polar covalent
- >1.7=ionic
- Exceptions: NaI & KI
- Bigger the difference, greater the attraction (Cs & F)
Ionic compounds: Positive ions and negative ions (non-directional)
- Held together by opposite charge attract
- Cations are oxidized, anions are reduced (with more electrons, charge is reduced)
o Share stable noble gas arrangements (don’t react)
Removal of electrons from atoms and ions requires energy, so ionization is an endo process.
- Question about force
Metals lose e B/c of metals low EN, and non-metals gain e b/c non-metals high EN
Same charges repel and opposite charges attract in a lattice (net attractive force)
- All lattices arrange differently to minimize repulsion
Example:
o NaCl-6:6 (coordination numbers)
o CsCl-8:8
Coulomb’s Law explains the force of attraction of ionic compounds (electrostatic force)
- Force is proportional to magnitude of charge and inversely proportional to the distance
o Consider Charge first and then consider Distance
Strength of ionic bond/force of the bond is determined by the bond/lattice dissociation energy (lattice
enthalpy)
- E required to decompose 1 mole of ionic lattice into gaseous ions
- More E, harder lattice
Ionic compounds are giant structu...
