Types of Non- Bonded Interactions Interaction "ion Interaction A hydrogen atom covalently bonded to N, O, or F is attracted to the lone pair of a different atom nearby H-bonding rming a hydrogen bond. 2k/mol Dispersion/London ydrogen bonding is stronger than any other non- bonds/interaction, yet weaker than covalent Induced dipole Hydrogen bonding Hydrogen bond o covalent HF(g) covalent Hydrogen bonding Variation of ionic radii with Some general trends for Ionic radii Coordination Number 1. lonic radii increase on going down a group (Lanthanide contraction restricts the increase of heavy 2. Radii of equal charge ions decrease across a period 3. lonic radii increase with increasing coordination lumber (the higher its CN the bigger the ions seems to The radius of one ion has to be 4. The ionic radius of a given atom decreases with fixed to a reasonable value increasing charge(r(Fe2+)>rFe3+)) (O2)=1.40A→ Linus 5. Cations are usually the smaller ions in a cation/anion That value is then combination(exceptions: r(Cs*)>r(F).1 compile a set of self 6. Frequently used for rationalization of structures nt values for all other oolA rcation)/r(anion)(< 1) 81012 Ion bond and Ion Crystal ome Properties of lonic Crystals Some Properties of lon Crystal rElative stable and hard crystals Lattice energy of ion crystal Poor electrical conductors (lack of free electrons) Ionic radii in crystals High melting and vaporization temperatures ← Pauling' s Rule Transparent to visible light but absorb strongly on bonds with part covalent bond infrared light n water and polar liquids3 Hydrogen bonding: A hydrogen atom covalently bonded to N, O, or F is attracted to the lone pair of a different atom nearby forming a hydrogen bond. Hydrogen bonding is stronger than any other non￾bonded interaction, yet weaker than covalent bonds/ionic bonds O H H .. H O H Hydrogen bond Types of Non-Bonded Interactions Interaction Energy Ion-ion interaction ~250 kJ/mol H-bonding ~20 kJ/mol Ion-dipole Dipole-dipole ~2 kJ/mol Dispersion/London <2 kJ/mol Induced dipole Examples: Compound/element Type Dominant Interaction NaH ionic Ion-ion ClBr covalent Dipole-dipole Rn noble gas Dispersion NH3 covalent Hydrogen bonding NH4Cl ionic Ion-ion HBr(g) covalent Dipole-dipole HF(g) covalent Hydrogen bonding Variation of Ionic Radii With Coordination Number The radius of one ion has to be fixed to a reasonable value (r(O2- ) = 1.40Å) ® Linus Pauling. That value is then used to compile a set of self consistent values for all other ions. 1. Ionic radii increase on going down a group. (Lanthanide contraction restricts the increase of heavy ions !!) 2. Radii of equal charge ions decrease across a period 3. Ionic radii increase with increasing coordination number (the higher its CN the bigger the ions seems to be !!) 4. The ionic radius of a given atom decreases with increasing charge (r(Fe2+) > r(Fe3+)) 5. Cations are usually the smaller ions in a cation/anion combination (exceptions: r(Cs+) > r(F- ) ...!!!) 6. Frequently used for rationalization of structures: “radius ratio” r(cation)/r(anion) (< 1) Some General Trends for Ionic Radii Ion Bond and Ion Crystal Some Properties of Ion Crystal Lattice energy of ion crystals Ionic radii in crystals Pauling’s Rules Ion bonds with part covalent bond Some Properties of Ionic Crystals Relative stable and hard crystals Poor electrical conductors (lack of free electrons) High melting and vaporization temperatures Transparent to visible light but absorb strongly infrared light Soluble in water and polar liquids!