1. In Chemistry there are 3 types of bonds:
IONIC
COVALENT
METALLIC

2. IONS

3. What are ions?
Ions are charged particles.
They are formed when neutral atoms LOSE or GAIN electrons
Atoms with incomplete outer electron shells are unstable. By either gaining or losing electrons, atoms can obtain full outer electron shells and become stable.
IONS only form when atoms react. It is only when they react will they lose or gain electrons.

4. - +
If we “take away” the electron we’re left with just a positive charge: +
Metals (& hydrogen) lose electrons when they react to form positive ions +

5. - - +
If we add an electron we’re left with a negative charge: - - + -
Non-metals gain electrons when they react to form negative ions +

6. How is a sodium ion formed?
Sodium atom:
Sodium ion:
11 protons = +11
11 protons = +11
11 electrons = -11
10 electrons = -10
Total charge = 0
Total charge = +1 + Na Na
loses
1 electron
2.8.1
(partially full outer shell)
[2.8]
(full outer shell)

7. How is a magnesium ion formed?
Magnesium atom:
Magnesium ion:
12 protons = +12
12 protons = +12
12 electrons = -12
10 electrons = -10
Total charge = 0
Total charge = +2 2+ Mg Mg
loses
2 electrons
2.8.2
(partially full outer shell)
[2.8]2+
(full outer shell)

8. How is a fluoride ion formed?
Fluorine atom:
Fluoride ion:
9 protons = +9
9 protons = +9
9 electrons = -9
10 electrons = -10
Total charge = 0
Total charge = -1 - F F
gains 1 electron
2.7 (partially full outer shell)
[2.8]-
(full outer shell)

9. How is a sulfide ion formed?
Sulfur atom:
Sulfide ion:
16 protons = +16
16 protons = +16
16 electrons = -16
18 electrons = -18
Total charge = 0
Total charge = -2 2- S S
gains 2 electrons
2.8.6 (partially full outer shell)
[2.8.8]2-
(full outer shell)

10. What is a compound ion?
Ions can be made up of a single atom or a group of atoms. An ion made up of a group of atoms is called a compound ion.
What atoms are present in the following compound ions?
Ion
Formula
Charge
Atoms present O H
hydroxide
OH- -1 S O O O O
sulfate
SO42- -2
nitrate
NO3- -1 N O O O C O O O
carbonate
CO32- -2 N H H H H
ammonium
NH4+ +1

11. IONIC BONDING

12. What Is An Ionic Bond
It is the electrostatic forces of attraction between oppositely charged ions
Ionic bond + -
NOTE:
In an ionic bond the electrons are always transferred from the metal to the non-metal

13. DOT AND CROSS DIAGRAMS FOR IONIC BONDS

14. SODIUM CHLORIDE Na Cl
SODIUM ATOM
2,8,1
CHLORINE ATOM
2,8,7
Sodium transfers 1 electron to chlorine so both atoms will gain full outer shells

15. SODIUM CHLORIDE + Na Cl
SODIUM ION
2,8
CHLORIDE ION
2,8,8
both ions now have ‘full’ outer shells; ie they have the electronic configuration of a noble gas

16. The Formation of Sodium Chloride - Summary
Ions 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...

17. Cl Mg Cl CHLORINE ATOMS 2,8,7 MAGNESIUM ATOM 2,8,2 MAGNESIUM CHLORIDE
Magnesium transfers two electrons one to each chlorine

18. Cl Mg Cl CHLORIDE IONS 2,8,8 MAGNESIUM ION 2,8 MAGNESIUM CHLORIDE 1-2+ Mg
CHLORIDE IONS
2,8,8 1-
MAGNESIUM ION
2,8 Cl

19. MAGNESIUM OXIDE Mg O
MAGNESIUM ATOM
2,8,2
OXYGEN ATOM
2,6

20. MAGNESIUM OXIDE Mg O

21. MAGNESIUM OXIDE 2+ 2- Mg O
OXYGEN ION
2,8
MAGNESIUM ION
2,8

22. COVALENT BONDING

23. Covalent Bonding is when a pair of electrons are shared between two or more non-metals
In this type of bonding electrons are NOT transferred
Ions are NOT formed as metals are NOT involved
Dot & Cross Diagrams for covalent bonding look very different to that of ionic bonding.
This time the shells are overlapping and not separate
Electrons which are shared will be shown in the overlap

24. HYDROGEN H H
atoms share a pair of electrons to form a single covalent bond
A hydrogen MOLECULE is formed
Hydrogen atom needs one electron to complete its outer shell
Another hydrogen atom also needs one electron to complete its outer shell
WAYS TO REPRESENT THE MOLECULE
H H
H H
PRESSING THE SPACE BAR WILL ACTIVATE EACH STEP OF THE ANIMATION

25. HYDROGEN H H H H
both atoms need one electron to complete their outer shell
atoms share a pair of electrons to form a single covalent bond
DOT AND CROSS DIAGRAM
H H
H H

26. H Cl H Cl Cl H HYDROGEN CHLORIDE
atoms share a pair of electrons to form a single covalent bond
Chlorine atom needs one electron to complete its outer shell
Hydrogen atom also needs one electron to complete its outer shell
WAYS TO REPRESENT THE MOLECULE
H Cl
H Cl
PRESSING THE SPACE BAR WILL ACTIVATE EACH STEP OF THE ANIMATION

27. METHANE H
Each hydrogen atom needs 1 electron to complete its outer shell H C H
WAYS TO REPRESENT
THE MOLECULE
H C H H H
A carbon atom needs 4 electrons to complete its outer shell
Carbon shares all 4 of its electrons to form 4 single covalent bonds
PRESSING THE SPACE BAR WILL ACTIVATE EACH STEP OF THE ANIMATION

28. C C H H H C H H C H H H H H H H H H H METHANE
atom needs four electrons to complete its outer shell
each atom needs one electron to complete its outer shell
Carbon shares all 4 of its electrons to form 4 single covalent bonds H
H C H H
DOT AND CROSS DIAGRAM
H C H H

29. N H N H H N H H H H H AMMONIA WAYS TO REPRESENT THE MOLECULE
Each hydrogen atom needs one electron to complete its outer shell
H N H H
H N H H H
Nitrogen can only share 3 of its 5 electrons otherwise it will exceed the maximum of 8
A LONE PAIR REMAINS
Nitrogen atom needs 3 electrons to complete its outer shell
PRESSING THE SPACE BAR WILL ACTIVATE EACH STEP OF THE ANIMATION

30. N N H N H H N H H H H H H H H H AMMONIA
atom needs three electrons to complete its outer shell
each atom needs one electron to complete its outer shell
Nitrogen can only share 3 of its 5 electrons otherwise it will exceed the maximum of 8
A LONE PAIR REMAINS
H N H
H N H H H

31. WATER
Each hydrogen atom needs one electron to complete its outer shell H O
WAYS TO REPRESENT
THE MOLECULE H
H O H
H O
Oxygen can only share 2 of its 6 electrons otherwise it will exceed the maximum of 8
2 LONE PAIRS REMAIN
Oxygen atom needs 2 electrons to complete its outer shell
PRESSING THE SPACE BAR WILL ACTIVATE EACH STEP OF THE ANIMATION

32. WATER H O H O H H
atom needs two electrons to complete its outer shell
each atom needs one electron to complete its outer shell
Oxygen can only share 2 of its 6 electrons otherwise it will exceed the maximum of 8
TWO LONE PAIRS REMAIN
H O H
H O H

33. Multiple Covalent Bonds
In all the examples shown so far, the covalent bonds formed are single bonds, formed when one pair of electrons is shared between two atoms.
The following examples show how double and triple covalent bonds can be formed between atoms.
There are no known examples of quadruple covalent bonds.

34. OXYGEN O O O O
each atom needs two electrons to complete its outer shell
each oxygen shares 2 of its electrons to form a
DOUBLE COVALENT BOND
O O
This time 4 electrons are being shared between the oxygen atoms

35. Double Bonds in an Oxygen Molecule
Oxygen atoms form simple molecules (diatomic) by sharing single electrons.
Each oxygen atom has two spaces in its outer shell, and can share these with the other oxygen atom, which also donates two electrons to the bond.
The sharing of two pairs of electrons constitutes a double covalent bond.

36. Double Bonds in an Oxygen Molecule
The diagram shows the oxygen atoms sharing four electrons in total, forming a double covalent bond.
As a result of this sharing, both atoms effectively have a full outer shell of electrons.
An oxygen molecule, O2 is the result.

37. Triple Bonds in a Nitrogen Molecule
Nitrogen atoms form simple molecules (diatomic) by sharing single electrons.
Each nitrogen atom has three spaces in its outer shell, and can share these with the other nitrogen atom, which also donates three electrons to the bond.
The sharing of three pairs of electrons constitutes a triple covalent bond.

38. Triple Bonds in a Nitrogen Molecule
The diagram shows that the nitrogen atoms can share six electrons in total, forming a triple covalent bond.
As a result of this sharing, both atoms effectively have a full outer shell of electrons.
A nitrogen molecule, N2 is the result.
This bond is one of the strongest covalent bonds in nature.

39. Example 2 X X X O C O X
O=C=O X X X X X X X X
This is a double bond as each atom shares 2 pairs of electrons to each gain 8 electrons in their outer shell.

40. METALLIC BONDING

41. METALLIC BONDING This type of bonding always occurs in metals ONLY
A metallic bond is the electrostatic force of attraction between the delocalised electrons and the positive metal ions (cations)

42. Free delocalised electrons
Metal atoms lose electrons to become POSITIVE IONS
Free delocalised electrons
In a metal the atoms LOSE SEVERAL OF THEIR OUTER ELECTRONS which drift around between the metal ions as FREE ELECTRONS.

43. As they have LOST a few electrons, the atoms become POSITIVE IONS
In a metal the atoms LOSE SEVERAL OF THEIR OUTER ELECTRONS which drift around between the metal ions as FREE ELECTRONS.
As they have LOST a few electrons, the atoms become POSITIVE IONS
Metal atoms. Notice all the atoms are the same size i.e. same atom of an element. This makes the structure regular
Free (“delocalised”) electrons