DEFINITION · Shielding remains constant ... other’s effects ... Are much weaker than covalent bonds Are easily overcome by heat. There are three types of intermolecular bond Van

DEFINITION

The electrostatic force of attraction between oppositely charged ions

Usually occurs when a metal bonds with a non-metal

Ions are formed by complete electron transfer from the metal atoms to the non-metal atoms

Ions have a noble gas or other stable electronic configuration

DOT and CROSS DIAGRAM

[ Na ]+

[ Cl ]-


[ Ca ]2+

2[ Cl ]-


2[ Na ]+

[ O ]2-

Ionic compounds have a giant lattice structure




◦ High melting points

◦ May dissolve in water

◦ Solid does not conduct electricity

◦ Conduct electricity when molten or dissolved in water

DEFINITION

A shared pair of electrons

One provided by each atom joined by the bond

Usually occurs when atoms of two non-metals bond together

Atoms achieve a noble gas or other stable electronic configuration


Cl Cl


O O

DEFINITION

A shared pair of electrons

Both provided by only one of the bonded atoms

Occurs when there is an atom with a lone pair of electrons to donate and an atom with room to accept a lone pair

Once formed it is the same as a covalent bond

Atoms achieve a noble gas or other stable electronic configuration


H +

H N H

H

PRINCIPLES

Electron pairs repel each other as much as possible

Lone pairs repel more than bonding pairs

Multiple bonds behave like single bonds

Electron pairs repel each other as much as possible

Bonding pairs

Lone pairs

DiagramBond angle / 0

Name

2 0 180 Linear

3 0 120 Trigonal planar

4 0 109.5 Tetrahedral

6 0 90 Octahedral

Lone pairs repel more than bonding pairsBonding pairs

Lone pairs


Name

4 0 109.5 Tetrahedral

3 1 107 Pyramidal

2 2 105 Non-linear

Multiple bonds behave like single bonds

BondsLone pairs


Name

2 0 180 Linear

3 0 120 Trigonal planar

2 1 118 Non-linear

DEFINITION

The electrostatic attraction between

positive metal ions and

their delocalised valency electrons

Positive metal ions

Sea of delocalised electrons

Atoms achieve a noble gas or other stable electronic configuration by ionising

Metals have giant lattice structures

They conduct electricity as their delocalised electrons can move

Strength of metallic bonding depends on

Size of ionic charge

Number of delocalised electrons

Size of ion (ionic radius)

Melting point increases from Na to Al

Size of ionic charge increases

Number of delocalised electrons increases

Size of ion (ionic radius) decreases

Melting point decreases from Li to Cs

Size of ionic charge stays the same

Number of delocalised electrons stays the same

Size of ion (ionic radius) increases

When the electrons are further from the centres of positive charge in the ions, the electrostatic forces of attraction are weaker

DEFINITION

The ability of an atom to attract the bonding electrons of a covalent bond

The most electronegative element is fluorine

Electronegativity increases on crossing a period from left to right

Nuclear charge (number of protons) increases

Atomic radius decreases

Shielding remains constant

Thus it becomes easier to attract the electrons of the bond

Electronegativity decreases on descending a group

Nuclear charge (number of protons) increases

Atomic radius increases

Shielding increases

Thus it becomes more difficult to attract the electrons of the bond

DEFINITION

A shared pair of electrons between atoms with different electronegativities

The more electronegative atom attracts the electrons and becomes a bit negative

The other atom is left a bit positive

Molecules have a permanent dipole (two poles)

H Cl

Cl -

C +

Cl -

-Cl

Cl -

CCl4 has four polar covalent bonds

The molecules are not polar

The polar bonds cancel out each other’s effects

N -

H +

+H

H +

O -

+H

H +

NH3 and H2O have polar covalent bonds

The molecules are also polar

The polar bonds do not cancel out each other’s effects

Exist between covalent molecules

Are much weaker than covalent bonds

Are easily overcome by heat

There are three types of intermolecular bond

Van der Waals’ forces – the weakest

Permanent dipole / permanent dipole interactions

Hydrogen bonds – the strongest

DESCRIPTION

Electrostatic forces of attraction between molecules or atoms in which the movement of electrons around the nuclei produces temporary induced dipoles

Movement of electrons in one atom causes a temporary dipole

This dipole induces another dipole in a nearby atom

There is weak attraction between the dipoles

Bigger molecules have more temporary induced dipoles, stronger van der Waals’ forces and higher boiling points

Boiling point increases from Cl2 to I2

Size of molecules increases

Number of electrons increases

More temporary induced dipoles occur

Strength of van der Waals’ forces increases

DESCRIPTION

Electrostatic forces of attraction between the oppositely charged ends of molecules with permanent dipoles

weak force of attraction

H Cl H Cl

These are in addition to van der Waals’ forces

They are stronger than van der Waals’ forces, need more energy to overcome so molecules have slightly higher boiling points

Occur between molecules where N, O or F are joined to H

N, O and F are more electronegative than H and attract the electrons of the bonds to H making it electron deficient +

The highly electronegative atom donates its lone pair of electrons to form a bond to an electron deficient hydrogen atom in an adjacent molecule.

O

H H

Hydrogen bond

O

H H

These are in addition to van der Waals’ forces

They are much stronger than van der Waals’ forces so molecules have much higher boiling points

Water has abnormally high melting and boiling points due to hydrogen bonding

Bonding Ionic

Structure Giant lattice

Melting pointBoiling point

High due to strong electrostatic forces of attraction between ions in the lattice

SolubilityDissolves in waterThe polar water molecules are attracted to the ions in the lattice

ConductivityThe solid does not conduct electricityNaCl conducts when molten or dissolved in water as the ions are free to move and carry charge

Bonding Metallic



High due to strong electrostatic forces of attraction between positive ions and the delocalised electrons in the lattice

Solubility Reacts with water

ConductivityThe solid conducts electricity as the delocalised electrons are free to move and carry charge

Bonding Covalent

Structure Simple molecular


Low due to the very weak van der Waals’ forces of attraction between molecules

Solubility Reacts with water

ConductivityDoes not conduct electricity at all as there are no mobile charged particles

Strong covalent bonds throughout the lattice

A tetrahedral arrangement of bonds around each carbon atom

Bond angles = 109.50

Bonding Covalent



High due to strong covalent bonds throughout the lattice

Hardness

HardThe tetrahedral arrangement of atoms enables external forces to be spread evenly throughout the lattice


A hexagonal layer structure

Strong covalent bonds within the layers

Bond angles = 1200

Weak van der Waals’ forces between the layers

Bonding Covalent



High due to strong covalent bonds throughout the lattice

Hardness

SoftBonding within each layer is strong but there are weak forces of attraction between the layers so they can slide over each other

ConductivityThe solid conducts electricity as the delocalised electrons between the layers are free to move and carry charge

Bonding Covalent

Structure Simple molecular


Relatively high due to the hydrogen bonds between moleculesHydrogen bonds are the strongest intermolecular bonds

Density

Lower than water Ice floats as it has an open crystal lattice in which the simple molecules are held apart by hydrogen bondsIn water, molecules pack closer together


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DEFINITION · Shielding remains constant ... other’s effects ... Are much weaker than covalent bonds Are easily overcome by heat. There are three types of intermolecular bond Van