chemistry (14 - 16) chemical bonding (ionic) © sser ltd

Chemistry(14 - 16)

Chemistry(14 - 16)

Chemical Bonding(Ionic)

Chemical Bonding(Ionic)

© SSER Ltd. © SSER Ltd.

They are usually hard crystalline solids with high melting points, e.g. CsCl has a melting point of 646 ºC.They are usually hard crystalline solids with high melting points, e.g. CsCl has a melting point of 646 ºC.

Ionic compounds are made up of giant structures between metals and non-metals.Ionic compounds are made up of giant structures between metals and non-metals.

Ionic CompoundsIonic Compounds

The ions exert strong electrostatic attractions within the lattice - this attraction is called IONIC BONDING.The ions exert strong electrostatic attractions within the lattice - this attraction is called IONIC BONDING.

Ionic CompoundsIonic Compounds

The elements react in an attempt to become more stable.The elements react in an attempt to become more stable.

The ions are formed when the elements react with one another.The ions are formed when the elements react with one another.

The crystalline shape reflects the internal symmetry in which millions of particles are arranged in a regular lattice structure.

The crystalline shape reflects the internal symmetry in which millions of particles are arranged in a regular lattice structure.

The different particles have opposite charges and arecalled ions.

The different particles have opposite charges and arecalled ions.

The Formation of IonsThe Formation of IonsIons are formed when one atom pulls the electron(s) completely away from another atom, giving both atoms a full outer shell of electrons. This gives a much more stable structure.

The Formation of IonsThe Formation of IonsIons are formed when one atom pulls the electron(s) completely away from another atom, giving both atoms a full outer shell of electrons. This gives a much more stable structure.

I II III IV V VI VII 0

The Formation of IonsThe Formation of Ions

Li

The ion hasa 1+ charge.

Na

K

Rb

Cs

Fr

All Group 1 elements readily lose one electron to complete their outer electron shell, giving a noble gas electronic configuration.As a result of the ease with which all the Group 1 elements lose an electron, they have similar chemical properties, i.e.react with Halogens forming ionic compounds in which the Group 1 ion has a single positive charge.

The Formation of IonsThe Formation of Ions

All Group 7 elements readily accept one electron to complete their outer electron shell, giving a noble gas electronic configuration.

The ion has a 1- charge.

As a result of the ease with which all the Group 7 elements accept an extra electron, they have similar chemical properties, i.e. react with alkali metals forming ionic compounds in which the Group 7 ion has a single negative charge.

I II III IV V VI VII 0

F

Cl

Br

I

At

The sodium and chlorine atoms need full outer shells of electrons to achieve stability.The sodium atom has one electron in its outer shell.The chlorine atom has one space in its outer shell.

The Formation of Sodium ChlorideThe Formation of Sodium Chloride

Stability is achieved by the donation of an electron from the sodium atom to the chlorine atom, to form sodium chloride.This gives both ions a noble gas electronic configuration.

The Formation of Sodium ChlorideThe Formation of Sodium Chloride

The chlorine atom takes on an electronic configuration of 2,8,8 and becomes a negatively charged chloride ion (Cl-).

The sodium atom takes on an electronic configuration of 2,8and becomes a positively charged sodium ion (Na+).

-+

The Formation of Sodium ChlorideThe Formation of Sodium Chloride

The two ions strongly attract one another as a result of their opposite electrostatic charges.

A stable, ionic compound, sodium chloride (NaCl) is the product.

The Formation of Sodium ChlorideThe Formation of Sodium Chloride

The two ions can also be represented as follows:

The Formation of Sodium ChlorideThe Formation of Sodium Chloride

+_

The Formation of Sodium Chloride - SummaryThe Formation of Sodium Chloride - SummaryIons are formed when the chlorine atom pulls a single electron completely away from a sodium atom, giving both atoms a full outer shell of electrons. This gives a much more stable structure.

Start the animation to see how ionic sodium chloride is formed...

The Formation of Sodium Chloride - SummaryThe Formation of Sodium Chloride - SummaryIons are formed when the chlorine atom pulls a single electron completely away from a sodium atom, giving both atoms a full outer shell of electrons. This gives a much more stable structure.

Start the animation to see how ionic sodium chloride is formed...

When sodium and chlorine gas react together, a very stable ionic compound, sodium chloride (NaCl) is the product.

The Formation of Sodium ChlorideThe Formation of Sodium Chloride

When sodium and chlorine gas react together, a very stable ionic compound, sodium chloride (NaCl) is the product.

Na + Cl2 NaClWhat is needed to balance the equation?2 2

The Formation of Sodium ChlorideThe Formation of Sodium Chloride

Surface of the sodium

The diagram shows how sodium ions and chloride ions pack together in a single plane of a sodium chloride crystal.

The Formation of Sodium ChlorideThe Formation of Sodium Chloride

The forces of attraction between the ions act in all directions within the crystal structure.

Na+Cl- Na+

Na+ Na+

Na+ Na+

Na+Na+

Cl-

Cl- Cl-

Cl- Cl-

Cl- Cl-

This is a 3-D view of a ball and stick model of a sodium chloride lattice.

Key

The Formation of Sodium ChlorideThe Formation of Sodium Chloride

sodium ion

chloride ion

As more ions are added to the structure, the lattice takes shape.

Each ion has six nearest neighbour ions of opposite charge.

Sodium Chloride - Ionic Crystal Lattice Sodium Chloride - Ionic Crystal Lattice

This image shows a corner of the giant ionic lattice of NaCl.

Sodium Chloride - Ionic Crystal Lattice Sodium Chloride - Ionic Crystal Lattice

Sodium Chloride – Ionic Crystal LatticeSodium Chloride – Ionic Crystal Lattice

Crystals of sea salt (sodium chloride) magnified one hundred times.Crystals of sea salt (sodium chloride) magnified one hundred times.

Notice the cubic shape of the crystal in the centre of the photograph. The cubic shape of the crystal is directly due to the cubic lattice.Notice the cubic shape of the crystal in the centre of the photograph. The cubic shape of the crystal is directly due to the cubic lattice.

Magnesium and chlorine also form an ionic compound called magnesium chloride (MgCl2).

The Formation of Magnesium ChlorideThe Formation of Magnesium Chloride

The magnesium atom has two spare electrons in its outer shell.

Stability is achieved by the donation of an electron from the magnesium atom to each of the two chlorine atoms, giving the three ions a noble gas electronic configuration.

The magnesium atom now has an electronic configuration of 2,8 and becomes a dipositively charged magnesium ion.

The Formation of Magnesium ChlorideThe Formation of Magnesium ChlorideBoth chlorine atoms take up an electronic configuration of 2,8,8 and become negatively charged chloride ions.

The ions attract one another as a result of their opposite electrostatic charges. An ionic compound, magnesium chloride, Mg2+Cl-

2 is the product.

Therefore the formula of magnesium chloride is MgCl2.

- -2+

The Formation of Magnesium ChlorideThe Formation of Magnesium Chloride

When magnesium and chlorine react together a very stable ionic compound, magnesium chloride (MgCl2) is the product.

The Formation of Magnesium ChlorideThe Formation of Magnesium Chloride

When magnesium and chlorine react together a very stable ionic compound, magnesium chloride (MgCl2) is the product.

Mg + Cl2 MgCl2

The Formation of Magnesium ChlorideThe Formation of Magnesium Chloride

Surface of the magnesium

As calcium is in the same group of the Periodic Table as magnesium, calcium chloride is formed in a similar way to magnesium chloride.

The Formation of Calcium ChlorideThe Formation of Calcium Chloride

Stability is achieved by the donation of an electron from the calcium atom to each of the two chlorine atoms, giving the three ions a noble gas electronic configuration.

The ions attract one another as a result of their opposite electrostatic charges. An ionic compound, calcium chloride, Ca2+Cl-

2 is the product.

Therefore the formula of calcium chloride is CaCl2.

The Formation of Calcium ChlorideThe Formation of Calcium Chloride

This arrangement has been described as ‘metallic meat balls in a fluid electronic soup’. Our model of the lattice can now be changed from this... to this...

A more detailed model of a metal lattice describes the lattice as having an outer layer of mobile electrons which can jump from atom to atom.

Metal Lattice – Free ElectronsMetal Lattice – Free Electrons

Metal LatticeThe electron soup is a result of the delocalisation of the free electrons in the outer shells of each atom.

These delocalised electrons enable metals to conduct electricity.

The electron soup is a result of the delocalisation of the free electrons in the outer shells of each atom.

Metal Lattice

These delocalised electrons enable metals to conduct electricity.

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