Shapes and IMFs

Linear molecule - bond angle, lone pairs & bonding regions

• Bond angle: 180

• 0 lone pairs

• 2 bonding regions

Non-linear molecule - bond angle, lone pairs & bonding regions

• Bond angle: 104.5

• 2 lone pairs

• 2 bonding regions

Trigonal planar molecule - bond angle, lone pairs & bonding regions

• Bond angle: 120

• 0 lone pairs

• 3 bonding regions

Pyramidal molecule - bond angle, lone pairs & bonding regions

• Bond angle: 107

• 1 lone pair

• 3 bonding regions

Tetrahedral molecule - bond angle, lone pairs & bonding regions

• Bond angle: 109.5

• 0 lone pairs

• 4 bonding regions

Octahedral molecule - bond angle, lone pairs & bonding regions

• Bond angle: 90

• 0 lone pairs

• 6 bonding regions

Electronegativity

The attraction of a bonded atom for the pair of electrons in a covalent bond

What is the most electronegative element?

Fluorine

What type of IMF do polar molecules have?

Permanent dipole-dipole interactions

Why are some molecules polar?

• Difference in electronegativities or

• The molecule isn’t symmetrical

• So dipoles don’t cancel out

Hydrogen bonding

• Bond between Hydrogen and lone pair of oxygen, fluorine or nitrogen

• Strongest IMF

Why does ice float in water?

• H bonds hold water molecules apart in an open lattice structure

• The water molecules in ice are further apart than in water

• Solid ice is less dense than liquid water and floats

Why does water have high melting and boiling point even though it has a simple covalent structure?

• The Hydrogen bonds holding the water molecules apart need a lot of energy to overcome those bonds, than if it only had London forces

Describe the structure of solid simple molecular lattices

Covalently bonded molecules attracted to each other by weak intermolecular forces

Why do simple molecular lattices have low melting and boiling points?

The weak intermolecular forces require little amount of energy to overcome these bonds

Why are non-polar simple molecular substances soluble in non-polar solvents?

• Intermolecular forces form between the substance molecules and the solvent molecules

• Interactions weaken the IMFs in the lattice structure

• IMFs break and compound dissolves

Why are non-polar substances usually insoluble in polar solvents?

• Due to little interaction between the molecules in the lattice and the solvent molecules

• The intermolecular bonding is too strong within the polar solvent to be broken

Why can’t simple molecular structures conduct electricity in any state?

• They have no free electrons that can move around and carry charge