Bond types Bond type electron Electronegativity difference IonicDonate/take>1.7 Polar covalent Share Nonpolar covalent Share<0.6

Comparing ionic and covalent compounds Molecular compounds Ionic compounds smallest particles molecules cations and anions origin of bonding electron sharing electron transfer forces between particles strong bonds between atoms weak attractions between molecules strong attractions between anions and cations strong repulsions between ions of like charge elements present close on the periodic table widely separated on the periodic table metallic elements present rarelyusually electrical conductivity poor good, when melted or dissolved state at room temperature solid, liquid, or gas solid melting and boiling points lowerhigher other names covalent compounds salts

Metallic bonds Metals’ valence electrons can move about between metal ions. Metals’ valence electrons can move about between metal ions. These nonlocalized electrons give metals their conductivity, malleability and strength These nonlocalized electrons give metals their conductivity, malleability and strength

Intermolecular forces (van der Waals forces) London dispersion- instantaneous dipole moment -increases with mass -found between all molecules Dipole-dipole- increases with polarity Hydrogen bonding The stronger the intermolecular forces, the greater the melting and boiling points and viscosity will be. Viscosity- resistance to flow. stronger weaker

Lewis Dot Diagrams H 2 H  H  bond to form H:H Each bond uses an electron from each atom. To create a Lewis dot diagram Count the total valence electrons available. 2. Ensure each atom has an octet (or a pair for H)

Exceptions to the Octet Rule Less than 8: B & Be Less than 8: B & Be Expanded valence: elements in period 3 or higher bonding with highly electronegative elements like F, O, and Cl. Expanded valence: elements in period 3 or higher bonding with highly electronegative elements like F, O, and Cl. Odd no. of valence electrons Odd no. of valence electrons

Valence Shell Electron Pair Repulsion theory- electron pairs repel each other, so are oriented as far apart as possible. > > > > Unshared-unshared repulsion Unshared-shared repulsion Shared-shared repulsion

Molecule Total no. of electron pairs No. of shared pairs No. of unshared pairs Molecular shape

Molecule Total no. of electron pairs No. of shared pairs No. of unshared pairs Molecular shape

Bent 104.5° Trigonal pyramidal 107.3°

Polarity Molecule is polar if... there is a polar bond AND it is asymmetrical H + H + O - + H C H + O - + H C H + H H + H + H H + H + polar nonpolar

If a central atom is symmetrically surrounded by identical atoms, it will be nonpolar. If a central atom is symmetrically surrounded by identical atoms, it will be nonpolar. Ex: linearAB 2 Ex: linearAB 2 trigonal planarAB 3 trigonal planarAB 3 tetrahedral AB 4 tetrahedral AB 4 square planarAB 4 square planarAB 4 trigonal bipyramidal AB 5 trigonal bipyramidal AB 5 octahedralAB 6 octahedralAB 6

Hybridization The mixing of 2 or more orbitals of similar energies on the same atom to produce new orbitals of equal energies. The mixing of 2 or more orbitals of similar energies on the same atom to produce new orbitals of equal energies. C  _ C  _ 1s  2s 2p 1s  2s 2p    1s sp 3 tetrahedral tetrahedral 3 p orbitals were used

How many bonds and unshared pairs are around the central atom? This is the number of equal energy orbitals needed. How many bonds and unshared pairs are around the central atom? This is the number of equal energy orbitals needed. sp has 2 electron domains sp has 2 electron domains sp 2 has 3 electron domains sp 2 has 3 electron domains sp 3 has 4 electron domains sp 3 has 4 electron domains sp 3 d has 5 electron domains sp 3 d has 5 electron domains sp 3 d 2 has 6 electron domains sp 3 d 2 has 6 electron domains

Sigma bonds are along the bond axis. Pi bonds are sideways with parallel overlap.

Single bond: Single bond: 1 sigma bond 1 sigma bond Double bond: Double bond: 1 sigma, 1 pi bond 1 sigma, 1 pi bond Triple bond: Triple bond: 1 sigma, 2 pi bonds 1 sigma, 2 pi bonds

Coordinate covalent bonds The shared electrons are supplied by a single atom The shared electrons are supplied by a single atom H H + H H + H N H + H + H N H H N H + H + H N H H

Heat of fusion Heat of vaporization Heating Curve for Water

Calculate the enthalpy change for each stage, then total them. To get the ice to 0 ◦ C: ∆H = (10.0g)(2.09J/g·K)(25 ◦ K)=515J To melt the ice: ∆H = (10.0g)(334 J/g)=3340J To heat the water to 100 ◦ C: ∆H = (10.0g)(4.18J/g·K)(100 ◦ K)=4180J To vaporize the water: ∆H = (10.0g)(2260 J/g)=22600J To heat the water to 125 ◦ C: ∆H = (10.0g)(2.02 J/g·K)(25 ◦ K)=505J

Phase Diagram Critical point- beyond this, the gas and liquid phases become indistinguishable. Triple point- all three phases are at equilibrium

The effect of increasing temperature and Activation Energy As the temperature increases, the peak for the most probable KE is reduced, and more significantly, moves to the right to higher values so more particles have the highest KE values. At the higher temperature T2, a greater fraction of particles has the minimum KE to react.

Enthalpy of solution- ∆H sol The energy change during dissolving. For solids in liquids, usually endothermic (>0) For gases in liquids, usually exothermic (<0)

Henry’s Law The amount of a gas that will dissolve in a liquid at a given temperature varies directly with the partial pressure of that gas. The amount of a gas that will dissolve in a liquid at a given temperature varies directly with the partial pressure of that gas.

Concentrations Molarity (M) moles solute Molarity (M) moles solute L solution L solution Molality (m) moles solute Molality (m) moles solute kg solvent kg solvent % by mass g solute % by mass g solute g solution g solution Mole fraction moles of solute Mole fraction moles of solute moles of solution moles of solution

Colligative properties Properties determined by the number of particles in solution (rather than the type) Properties determined by the number of particles in solution (rather than the type) Vapor pressure decreases Vapor pressure decreases Boiling point increases Boiling point increases Freezing point decreases Freezing point decreases Osmotic pressure Osmotic pressure

vapor pressure Decreases (with a nonvolatile solute) Decreases (with a nonvolatile solute) P solution = x solvent ∙P solvent P solution = x solvent ∙P solvent Vapor pressure = (mole fraction) (vapor pressure) solution solvent solvent solution solvent solvent Raoult’s Law: vapor pressure of a solution varies directly as the mole fraction of the solvent.

Determining freezing/boiling point changes ∆T fp = m∙K fp molality x freezing point constant molality x freezing point constant ∆T bp = m∙K bp molality x boiling point constant molality x boiling point constant K fp for water is C°/1m water K bp for water is.515 C°/1m water For other substances, see table A-8 on p.860.

Determining molecular mass If 8.02g of solute in 861g water lowers the freezing point to °C, calculate the molecular mass of the solute. ∆T fp = m∙K fp so m = ∆T fp = °C =.232m K fp 1.853°C/m K fp 1.853°C/m 8.02g solute x 1 kg water = 40.1 g/mol.861kg water.232 mol solute