Chemistry: Structure & Bonding

Exothermic

Forming bonds, releasing energy and getting hotter, so enthalpy is negative

Endothermic

Breaking bonds, requiring energy and gets colder, so enthalpy is positive

Bf₃

BeCl₂

SO₂

Tetrahedral

Bond angle 109.5

Trigonal Planar

Bond angle 120

Linear

Bond angle 180

Bent (3 regions)

Bond angle 120

Trigonal Pyramidal

Bond angle 109.5

Bent (4 regions)

Bond angle 109.5

Electronegativity

Fluorine is the most electro negative - the more right you travel on the periodic table, the more electronegative

“Like dissolves like” → Polar dissolve polar, Non-polar dissolves non-polar

The strength of the solute-solvent attraction is strong enough the overcome the pre-existing solvent-solvent and solute-solute attraction.

Molecular: Particle

Molecules

Molecular: Bonding type

1. Weak, intermolecular forces

2. Strong, intramolecular covalent bonds

Molecular: Structure

Random arrangement

Molecular: Hardness

Soft, due to weak intermolecular forces

Molecular: MP + BP

Low MP and BP due to weak intermolecular forces

Molecular: Solubility

“Like dissolves like”

Molecular: Electrical Conductivity

No, due to lack of FMCP

Ionic: Particles

Ions

Ionic: Bonding type

Electrostatic ionic bonds (forces of attraction)

Ionic: Structure

Rigid regular 3d lattice of alternating anions and cations held together by strong electrostatic ionic bonds

Ionic: Hardness

Hard, but brittle

Ionic: MP + BP

High MP and BP, approx. 500 - 1000 celsius

Ionic: Solubility

Soluble in polar solvent

Ionic: Electrical Conductivity

No in solid form due to lack of FMCP, Yes once dissolved.

Metallic: Particles

Atoms

Metallic: Bonding types

Sea of delocalized electrons (valence, non-directional)

Metallic: Structure

Regular 3d lattice of metal cations in a sea of delocalized electrons held together by strong, non-directional metallic bonding, organized

Metallic: Hardness

Ranges depending on type of metal, malleable and ductile

Metallic: MP+BP

Generally high MP and BP due to strong metallic bonds, except alkali metals

Metallic: Solubility

Not at all

Metallic: Electrical Conductivity

Yes - solid and molten forms can, due to the sea of delocalized electrons

Covalent Networks: Particles

Atoms *

Covalent Networks: Bonding types

Covalent bonds

Covalent Networks: Structure

3d: covalently bonded into a tetrahedral lattice

2d: covalently bonded into a trigonal planar lattice with delocalized electrons

Covalent Networks: Hardness

3d: Hard, strong covalent bonds

Graphite: soft due to weak intermolecular forces

Covalent Networks: MP + BP

Extremely high MP and BP, over 3000 celsius

Covalent Networks: Solubility

Not at all *

Covalent Networks: Electrical Conductivity

2d: Yes as it has FMCP

3d: No as it doesn’t have FMCP

Intramolecular vs. Intermolecular

Intra - inside molecules

Inter - holds multiple bonds together

Examples of Covalent Networks

Graphite - 2d

Diamond - 3d

Silica - 3d

Ionic solids are…

Metal + non-metal bonded together eg. NH_{4 ⁺} and NaCl