# data[].attributes.headline
Formation of a covalent bond - Potential Energy Profile

# data[].attributes.subject
Formation of a covalent bond - Potential Energy Profile

# data[].attributes.body
Larger molecules (like Br₂ and I₂) have shallower energy dips because their bond dissociation energies are lower than those of smaller ones (H₂ and Cl₂).

Atomic size increases down the group, leading to longer bond lengths and more diffuse valence orbitals.

Orbital overlap is less effective in larger atoms due to greater distance and poorer concentration of electron density in the bonding region.

Weaker bonds result, causing less stabilization and a shallower potential energy minimum on the curve.

# data[].attributes.body
COVALENT BONDING

# data[].attributes.body
The shapes of molecules are determined using valence shell electron pair repulsion theory (VSEPR) - it looks at the effects of repulsion between electrons and electron pairs and can be summarised into a few principles:

Molecular shape is determined by minimising repulsion between negative electron pairs.

Electron pairs will always occupy the geometrical shape that corresponds to the lowest energy configuration.

Bond pairs (BP) of electrons repel LESS than lone pairs (LP) due to being localised:
LPLP > BPLP > BPBP

# data[].attributes.attachment_link.title
What Shapes Do Simple Molecules Make | Properties of Matter | Chemistry | FuseSchool

# data[].attributes.body
Molecule shapes

# data[].attributes.body
A dative covalent bond is a bond that is formed by the overlapping of orbitals and the sharing of an electron pair both of which belong to one atom.

The atom that contributes the electron pair (a lone pair) is electron rich - it is called the donor atom.

The atom that accepts the electron pair is electron deficient - it is called the electron acceptor.

Examples:
(a) ammonium ion (NH ₄⁺)
(b) hydronium ion (H ₃ O⁺) - example of oxonium ion (oxygen cation with 3 bonds)

# data[].attributes.body
Once a dative covalent bond is formed, there is no difference between it and an ordinary covalent bond. The electron pair involved is usually represented by an arrow.
Formation of the NH ₄+ ion shown below:

# data[].attributes.headline
The table below shows you how to determine the shape of a molecule by considering the:

# data[].attributes.subject
The table below shows you how to determine the shape of a molecule by considering the:

# data[].attributes.body
·    number of lone pair electrons

·    number of electron pairs (electron cloud regions)
You are expected to know the following molecule shapes: linear, angular, trigonal planar, trigonal pyramidal, tetrahedral, trigonal bipyramidal and octahedral.

# data[].attributes.headline
POLARITY: POLAR VS NON-POLAR VS. IONIC BONDS

# data[].attributes.subject
POLARITY: POLAR VS NON-POLAR VS. IONIC BONDS

# data[].attributes.attachment_link.title
The Chemical Bond: Covalent vs. Ionic and Polar vs. Nonpolar

# data[].attributes.headline
EXERCISE ON POLARITY, BOND ANGLE AND MOLECULE SHAPE

# data[].attributes.subject
EXERCISE ON POLARITY, BOND ANGLE AND MOLECULE SHAPE

# data[].attributes.body
Do these questions

# data[].attributes.body
Answer Key:

# data[].attributes.body
Determine the difference in electronegativity values then decide the type of bond in the following list:

K₂S

PCl₃

I₂

HI

Answer key:

K₂S:

∆EN = 2.5-0.8 = 1.7

An ionic bond with polar covalent character

PCl3  ∆EN =
I2  ∆EN =
HI  ∆EN =

# data[].attributes.headline
CHEMICAL BONDS VS. INTERMOLECULAR FORCES

# data[].attributes.subject
CHEMICAL BONDS VS. INTERMOLECULAR FORCES

# data[].attributes.body
There is a distinction between chemical bonds and intermolecular forces.

Intramolecular forces = the forces that exist within a molecule (holding atoms together), these are proper chemical bonds.

Intermolecular forces = the forces that exist between molecules.

Intermolecular forces (IMF's) determine the melting and boiling points of substances.

# data[].attributes.headline
Two kinds of forces operate in a molecule—intramolecular vs. intermolecular forces:

# data[].attributes.subject
Two kinds of forces operate in a molecule—intramolecular vs. intermolecular forces:

# data[].attributes.body
Let's try to understand this difference through the following example:

1. You have six towels— Three are blue in colour labeled hydrogen, and three are pink in colour labeled chlorine.

2. You are given a sewing needle and thread to sew one hydrogen towel to one chlorine towel.

3. After sewing, you have three pairs of towels: hydrogen sewed to chlorine.

4. The next step is to attach these three pairs of towels to each other with Velcro.

5.  Now, pull this assembly from both ends: what do you think will happen?

6. Imagine the towels to be real atoms, such as hydrogen and chlorine.

These two atoms are bound to each other through a polar covalent bond—analogous to the thread.

Each hydrogen chloride molecule in turn is bonded to the neighboring hydrogen chloride molecule through an intermolecular attraction—analogous to Velcro.

# data[].attributes.headline
INTERMOLECULAR FORCES - EXIST BETWEEN MOLECULES

# data[].attributes.subject
INTERMOLECULAR FORCES - EXIST BETWEEN MOLECULES

# data[].attributes.body
A short summary of some of the different types of IMF's:

# data[].attributes.body
London forces occur between non-polar molecules.

Electrons are mobile in the orbitals of a molecule so that at any given moment it is possible that there is an uneven distribution of electrons in the molecule giving it a temporary dipole.

This momentary dipole can induce a temporary dipole in a neighbouring molecule resulting in a temporary weak attraction known as a London force.

The strength of London forces between molecules increases with:

increased number of electrons (which leads to greater polarizability)

increased size of electron cloud (“increased molecular mass” as generic statement results in a larger electron cloud that is more easily polarized)

increased surface area (linear isomers have stronger London forces than branched isomers due to greater contact between molecules)

# data[].attributes.body
This exists between polar molecules (molecules which are dipoles), e.g. between HCl molecules:

# data[].attributes.body
Hydrogen bonding is a special type of dipole-dipole attraction and are only found when:

i)   hydrogen is covalently bonded to a small and highly electronegative nitrogen,

oxygen or fluorine atom.

ii)  there is at least one lone pair on the N, O or F.

e.g. HF,   H₂O,   NH₃,   (plus all alcohols and carboxylic acids)

# data[].attributes.headline
Hydrogen Bonding Evidence from Boiling Points of the Hydrides

# data[].attributes.subject
Hydrogen Bonding Evidence from Boiling Points of the Hydrides

# data[].attributes.body
Explain the trend for H2O, NH3 and HF:

# data[].attributes.body
BETWEEN IONS OF A SALT DISSOLVED IN A SOLVENT

# data[].attributes.body
E.G. In blood between iron ion and oxygen

# data[].attributes.body
List all types of IMFs that would occur in each of the following:
a. CH ₃ CF 3
b. CCl 4
c.     SO ₂
d.     BrF
e.     CO ₂
f.      NH ₃
g.     Salt water
h.     Iron ions in your blood, transporting oxygen gas

# data[].attributes.headline
INTERMOLECULAR FORCES AND PROPERTIES DUE TO IMF's

# data[].attributes.subject
INTERMOLECULAR FORCES AND PROPERTIES DUE TO IMF's

# data[].attributes.body
2021 notes

# data[].attributes.attachment_link.title
Intermolecular forces and properties Notes 2021

# data[].attributes.headline
Physical properties depend on the strength of intermolecular forces

# data[].attributes.subject
Physical properties depend on the strength of intermolecular forces

# data[].attributes.body
The stronger the forces between the molecules or particles:
(a)  the higher the melting point
(b) the higher the boiling point
(c) the lower the vapor pressure
(d) the higher  the viscosity
(e) the higher the surface tension

# data[].attributes.headline
Properties of water due to hydrogen bonding 

# data[].attributes.subject
Properties of water due to hydrogen bonding 

# data[].attributes.body
High surface tension

High heat capacity

Capillary action due to cohesion and adhesion forces

Density change due to change in temperature

# data[].attributes.body
Consider the following list of substances.
KBr (s)     CCl₄ (l)      NH₃ (g)      HCl (g)        Pb (s)        Ar (g)        Cl₂ (g)

Select the substance which best matches the following descriptions: 1
1 A monatomic substance with London forces between its particles.
2 An excellent conductor of electricity, except in the solid phase.
3 A good solvent for non-polar solids.
4 A good example of a substance in which hydrogen bonds are found.
5 Contains dipole – dipole forces between its molecules.
6 Are non-polar molecules.
7 Contains delocalized electrons.
8 Ionic bonds hold the crystal lattice together.

# data[].attributes.headline
Why do substances dissolve (are miscible)?

# data[].attributes.subject
Why do substances dissolve (are miscible)?

# data[].attributes.body
1. When a solute dissolves, it’s particles proceed towards a state of greater DISORDER.

2. At the same time the solvent (a pure homogeneous substance) also becomes mixed with particles of a different kind.

3. There is an overall increase in disorder (called entropy), which is the driving force in the dissolution process.

4. Despite this increase in disorder, which aids dissolution, not all substances dissolve.

5. Two substances mix perfectly into solution (i.e. dissolve) if:

INTERMOLECULAR FORCES between the molecules/ions of the substance are OVERCOME.

Therefore, when the forces between the molecules of the solute and solvent are of the same ORDER OF MAGNITUDE, then the molecules of the solvent can take the place of the molecules of the solute.

The result is MIXING.

LIKE DISSOLVES LIKE.

Molecular crystals dissolve in non-polar solvents => solute forms Van der Waals LONDON Forces with solvent.

Ionic compounds dissolve in polar solvents => ions of solute form ION-DIPOLE interactions with solvent.

# data[].attributes.attachment_link.title
Intermolecular forces animation and explanation

# data[].attributes.body
Watch this video for recap of the topic:

# data[].attributes.headline
INTERPARTICLE FORCES IN SOLIDS - SUMMARY

# data[].attributes.subject
INTERPARTICLE FORCES IN SOLIDS - SUMMARY

# data[].attributes.body
Generally referred to as "intermolecular" forces, although:

network solids have interatomic forces between atoms forming a network

ionic solids (salts) have interionic forces between ions forming a crystal structure

metallic solids have electrostatic forces between cations & delocalised electron in a metal crystal structure

# data[].attributes.body
A network solid is a solid in which atoms are bonded by strong covalent bonds in a continuous network extending throughout the material. The entire crystal is considered to be a macromolecule (a giant molecule).
These giant molecules can be:
• Plate-like, e.g. graphite
• Three dimensional, e.g. diamond and silicon dioxide

The strong covalent bonds between the carbon atoms explain the hardness, chemical stability and very high melting points of these network solids.

# data[].attributes.body
Diamond cannot conduct electricity, because it has no free electrons in its giant structure.

Graphite can conduct electricity, because it has free (mobile) electrons in its giant structure.

# data[].attributes.attachment_link.title
The difference between diamond and graphite, giant covalent structures

# data[].attributes.attachment_link.title
4.3 Describe the structure of and bonding in silicon and silicon dioxide [SL IB Chemistry]

# data[].attributes.body
Covalent vs ionic vs metallic bonding

# data[].attributes.headline
INTERMOLECULAR FORCES - ADDITIONAL NOTES

# data[].attributes.subject
INTERMOLECULAR FORCES - ADDITIONAL NOTES