S2 Chemistry HL

Define Ionic bonding

Electrostatic attraction between oppositely charged ions

Define Covalent bonding

Electrostatic attraction between a shared pair and positively charged nuclei.

Define Metallic bonding

Electrostatic attraction between a lattice of cations and a sea of delocalised electrons

Properties of Ionic bonding

High melting points, low volatility, generally high solubility (in polar compounds), high conductivity (when molten), high brittleness

Properties of Covalent bonding

Low melting point, high volatility, low solubility, poor conductivity, high brittleness

Properties of Metallic bonding

High melting points, low volatility, very low solubility, high conductivity, high malleability and ductility.

Volatility

A substance’s tendency to vaporise

Solubility

The ability of a substance to dissolve another substance to form a uniform mixture/solution

Conductivity

The ability of charged particles to move through a region of space

Brittleness

a material's tendency to fracture or shatter suddenly under stress with little to no plastic (permanent) deformation.

Malleability

Ability to be bent/reshaped when compressed

Ductility

Ability to be drawn out into wire when stretched

Bond polarity

Results from the difference electronegativities

Polarity

Related to the way electrons are distributed within molecules/bonds

Molecular polarity

describes electron distribution throughout whole molecules

Polar molecules

When the electron distribution leads to a partial negative charge on one end of the molecule and a partial positive on the other. Creating a dipole moment, (In other words they look asymmetrical)

Intermolecular forces

Electrostatic forces of attraction that keep molecules together

London dispersion forces

Temporary induced dipole via random electron movement.

Occur in all molecules

LDF Examples

He, Ne, Ar, Kr, O2, N2, I2, Cl2, CH4, C2H6, CO2

Dipole induced dipole

The presence of a permanent dipole in the polar molecule induced the formation of temporary dipole in the neighbouring non-polar molecule

Between polar and non-polar molecules

Dipole Induced Dipole examples

O2, I2, HCL, Ar

Dipole Dipole

When a molecule is polar, it has a permanent dipole, therefore experiences dipole-dipole forces of attraction with neighbouring polar molecules

Between polar molecules ONLY

Hydrogen bonding

Intermolecular attraction between two molecules which contain a hydrogen bond to a highly negative element like F,O,N

Van Der Waal Forces

LDF/Dipole-Dipole/Dipole-induced Dipole

Order of IMF (weakest-strongest)

LDF → D-ID→ D-D→ H bonds → Ionic/Covalent

Covalent network structures

Vast/continuous 3D structures linked via strong covalent bonds/extreme hardness/high melting points

Allotropes + arrangement

Diamond (tetrahedral) / Graphite (C atom bonded to 3 other c atoms) / Graphene (one layer of graphite

Resonance bonds AHL

Two or more possible resonance structures to represent a molecule

Hybridisation AHL

Concept of mixing atomic orbitals to form new hybrid orbitals of new shapes

Electron geometry

determined by the total number of electron domains (both bonded pairs and lone pairs) surrounding a central atom

Molecular Geometry

Describes the arrangement of only the atoms, ignoring lone pairs, resulting in the molecule's actual 3D shape

EG:Linear (2)

2 pairs
No lone pairs = Linear
1 lone pair = Linear

EG: Trigonal Planar (3)

3 e groups
0 lone pairs = Trigonal Planar
1 lone pairs = Angular

EG: Tetrahedral (4)

4 be- groups

0 lone pairs

BA: 109.5

MG: Tetrahedral
OR

3 be-groups

1 lone pair

<109.5

MG: trigonal pyramidal

OR

2 be- groups

2 lone pairs

«109.5

MG: bent

EG: Trigonal bipyramidal (5)

5 be- groups

0 lone pairs

BA: 120 (équatorial)/ 90 (axial)

MG: Trigonal bipyramidal

OR

4 be- groups

1 lone pairs

BA: <120 (équatorial)/ <90 (axial)

MG: Seesaw

OR

3 be- groups

2 lone paris

BA: <90

MG: T shaped

Or

2 be- groups

3 lone pairs

BA: 190

MG: Linear

EG: Octahedral (6)

6 Be- groups

0 Lone pairs

BA: 90

MG: Octahedral

OR
5 Be- groups

1 lone pair

BA: <90

MG: square pyramidal

OR

4 Be- groups

2 lone pairs

BA: 90

MG: square planar