1. C3 Atoms,elements and compounds
3.4 Ions & ionic bonds

2. Learning objectives
Describe the formation of ions by electron loss or gain.
Describe the formation of ionic bonds between metals and non-metals as exemplified by elements from Group 1 and V11.
Supplement:
Explain the formation of ionic bonds between metallic & non-metallic elements.
Describe the lattice structure of ionic compounds as a regular arrangement of alternating positive & negative ions, exemplified by the sodium chloride structure.

3. C H O H2O CO2 Na+ Cl2 K+ OH– Mg CH4 atom ion molecule
Which are atoms, ions or molecules?
Put the following particles into the correct column of the table.
C H O H2O
CO Na+
Cl K OH– Mg CH4
atom
ion
molecule

4. C3b: How Atoms Combine – Ionic Bonding
Ions
An ion is a charged atom or group of atoms
For example:
Cl-, Mg2+, Na+ , SO4
These are all ions because they carry a positive (+) or negative (-) charge. 2-

5. How are Ions formed? Ions are formed when atoms gain or lose electrons
Positive ions are formed when atoms lose electrons
Negative ions are formed when atoms gain electrons

6. Positive and Negative ions
Positive ions are formed by the loss of electrons from atoms e.g.:
2+ ions form by the loss of 2 electrons
Negative ions are formed by the gain of electrons by atoms:
2- ion formed by the gain of 2 electrons
Look at the 2 following examples …

7. For e.g. Magnesium Mg Mg has 12 electrons Electron arrangement:26
Mg has 12 electrons
Electron arrangement:
2, 8, 2
Mg will lose two electrons to form 2, 8
Therefore Mg will have 12 protons and 10 electrons and will an overall +2 charge
Mg  Mg+2 Mg 12

8. For e.g. Chlorine Cl Cl has 17 electrons Electron arrangement: 2, 8, 7
35.5
Cl has 17 electrons
Electron arrangement:
2, 8, 7
Cl will gain one electron to form 2, 8, 8
Therefore Cl will have 17 protons and 18 electrons and will an overall -1 charge
Cl  Cl-1 Cl 17

9. This is called an ion (in this case, a positive hydrogen ion)
Ions
An ion is formed when an atom gains or loses electrons and becomes charged: + -
The electron is negatively charged
The proton is positively charged + +
If we “take away” the electron we’re left with just a positive charge:
This is called an ion (in this case, a positive hydrogen ion)

10. The Electrons in a Sodium Ion
In the sodium atom
Atomic number = number of protons = 11
Number of electrons = 11 23 Na 11
Na+ Na
Bye!
Electron lost
Electron arrangement: (Incomplete Shell)
Electron arrangement: 2.8 (Full Shells)

11. Stable octet
When atoms gain or lose electrons to get a complete outer shell they are stable (a stable octet)
They mimic a noble gas arrangement of electron configuration

12. Try to draw the formulae of the ion for each atom and then one person can check on the board (Right click and zoom for bigger animation)

13. What do you notice? Any pattern?

14. Types of bonding Atoms can be joined together in 3 possible ways
Metal and non-metal
Non-metals only
Metals only
Ionic Bonding
Covalent Bonding
Metallic Bonding
All three types involve changes in the electrons in the outermost electron shells of the atoms

15. IONIC BONDING
Support sheet for foundation: Collins’ Worksheet C3b 2 (Look in this sheet ‘O_C3b_1.doc’
Support sheet for higher: First 3 pages of Ionic and covalent bonding worksheet.doc

16. Ionic Bonding Happens between metals and non-metals
Involves electron transfer
This forms ions – positive & negative
Full outer shells are formed
Resulting in a stable structure
The positive and negative charges (attractions) constitute the ionic bond

17. Consider this reaction:
Lithium + Fluorine
Lithium Fluoride
How is Lithium Fluoride bonded ?

18. Same number of protons and electrons Both atoms are neutral
Lithium Li 7 3
Fluorine F 19 9
9p+
10n
Same number of protons and electrons
Both atoms
are neutral
3p+ 4n
3 protons +
3 electrons –
0 charge
9 protons +
9 electrons –
0 charge
3 protons +
2 electrons –
+1 charge
9 protons +
10 electrons –
-1 charge

19. He (He:2) Ne (Ne:2,8) FULL OUTER SHELLS ARE MADE, with
NOBLE GAS CONFIGURATION He 2 4
(He:2)
3p+ 4n
Lithium ion (Li1+) has same electron configuration as Helium
9p+
10n Ne 10 20
(Ne:2,8)
Fluoride ion (F1-) has same electron configuration as Neon

20. The ions are held together by electrostatic attraction:
3p+ 4n + -
9p+
10n
Li+ F-
This is a stable ionic compound

21. “Dot and cross” model for the ionic bonding in sodium chloride

22. Formation of sodium chloride 1. Formation of sodium ions
Sodium has 1 electron in its outer shell.
If it loses this it will have no partially filled shells. Na
Na+
Loses 1 electron
Sodium atom (2.8.1)
Sodium 1+ ion (2.8.0)
This only happens if there is another atom able to accommodate the lost electron.

23. Formation of sodium chloride 2.Formation of Chloride ions
Chlorine has 7 electrons in its outer shell.
If it gains 1 electron it can achieve a full outer electron shell. It is, therefore, going to be able to accept the electron that the sodium wants to lose. Cl Cl
Gains 1 electron
(from sodium)
Chlorine atom (2.8.7)
Chlorine I - ion (2.8.8)

24. Formation of Sodium Chloride- the overall process.
Sodium loses its
outer electron.
Chlorine gains it.
The result is
both end up with
full shells Cl Na
Two oppositely
charged ions
are formed,
which attract.
Millions of such pairs form a giant lattice Na Cl

25. Simpler electron diagrams
We can assume full inner electron shells.
We can therefore sometimes shorten bonding diagrams by omitting to draw the inner electron shells. Na Cl Na Cl

26. sodium chloride magnesium oxide Sodium oxide magnesium chloride
Instruction
Foundation
For each of the following slides state the ions involved. State how many electrons is/are gained/lost by each ion
Higher
Draw dot and cross diagram for these compounds after looking through these slides: (show charges clearly)
sodium chloride magnesium oxide
Sodium oxide magnesium chloride
NaF
Li2O

27. “Dot and cross” model for the ionic bonding in magnesium oxide

28. Bonding in Magnesium Oxide
More than one electron may be transferred between atoms in ionic bonding. O Mg
2.8.2.
2.6
Magnesium atom
Oxygen atom
Mg2+
O2-
2.8
Magnesium Oxide

29. Questions sodium chloride – done magnesium oxide – done sodium oxide
magnesium chloride
NaF
Li2O
Draw dot & cross models for the bonding in sodium oxide and magnesium chloride

30. Sodium oxide ionic bonding Supplement learning objective!

31. The ions are held together by electrostatic attraction:+ + Na Na
- 2
Na= 2, 8
Na= 2, 8 O
Na2O
O= 2, 8

32. Magnesium chloride ionic bonding

33. The ions are held together by electrostatic attraction:Cl -
Cl= 2, 8, 8 Cl -
Cl= 2, 8, 8
+ 2 Mg
MgCl2
Mg= 2, 8

34. Another way of showing it …Cl -
Magnesium chloride: Cl Mg 2+ Mg + Cl - Cl
MgCl2

35. Activity
Following the previously shown slides draw bonding diagrams for the compounds formed from the following atoms:
Lithium (2.1) and fluorine (2.7)
Sodium (2.8.1) and sulphur (2.8.6)
Magnesium (2.8.2) and sulphur (2.8.6)
Magnesium (2.8.2) and fluorine (2.7)
Aluminium (2.8.3) and nitrogen (2.5)
Remember that the total number of electrons lost by the metal must equal the total number of electrons gained by the non-metal

36. • State the formulae for the ions NO3–; CO32–; SO42–; and NH4+.
Week 6
• Predict ionic charge from an element’s position in the Periodic Table.
• State the formulae for the ions NO3–; CO32–; SO42–; and NH4+.
- Use these in making compounds (predicting formulae for ionic compounds)
© Pearson Education Ltd 2008
This document may have been altered from the original

37. Fill in the formula of each compound in the table:
The following table will help you to work out the name of some important compounds. Try the first table, which is easier than the second one.
Fill in the formula of each compound in the table:
Chloride, Cl-
Bromide, Br-
Oxide, O2-
Sodium, Na+
NaCl
Magnesium, Mg2+
Aluminium, Al3+

38. Hint: Use brackets for ions made of group of atoms:
Hydroxide, OH-
Nitrate, NO3-
Carbonate, CO32-
Sulphate, SO42-
Sodium, Na+
Magnesium, Mg2+
Aluminium, Al3+
Ammonium, NH4+

39. Positive ions and negative ions attract one another

40. Ionic Bond Lattices are 3-Dimensional
Ions attract and build into a 2 dimensional sheet. + -
In fact the whole process will be going on in three dimensions to build up a giant 3-D lattice. + -
And so on to build a giant 3-D lattice with millions of ions. + -

41. Ionic solids like NaCl and MgO form:
Giant Ionic lattices are held together by strong ionic bonds, which means:
They have high melting & boiling points

42. Salt – Sodium Chloride
Common salt contains two ions: sodium (+) and chlorine (-).
These form giant ionic lattices in which positive ions are electrostatically attracted to negative ions.

43. Sodium Chloride structure

44. Properties of Sodium Chloride
Has a high melting point – due to strong ionic bonds
Dissolves in water
When solid does NOT conduct electricity
Sodium chloride solution conducts electricity.

45. Sodium chloride conducts electricity when dissolved in water

46. Magnesium Oxide
Common salt contains two ions: Magnesium (2+) and Oxide (2-).
Forms a giant ionic lattice in which positive ions are electrostatically attracted to negative ions.

47. Magnesium Oxide structure

48. Properties of Magnesium Oxide
Has a very high melting point – strong ionic bonds
When solid does NOT conduct electricity – ions cannot move
Magnesium oxide and sodium chloride conduct electricity when molten

49. Explaining the properties of NaCl and MgO
When ionic bonds in the lattices are broken, the solids MELT.
This means the ions are free to move & can conduct electricity.
Sometimes lattices can be broken by water molecules and the solids dissolve. Again the ions are free to move & can conduct electricity.

50. QUESTION ? Why does MgO have a higher melting point than NaCl ?
Why does NaCl dissolve in water, and
MgO does not ?
QUESTION ?
NaCl = Na+ Cl-
MgO = Mg2+ O2-
Greater force of attraction in MgO – 2+ & 2-
Therefore lattice strength is greater.

51. Practical: C3b solubility and conductivity
Experimental investigation of solubility and electrical conductivity of solids and solutions

52. Practical work F&H
(F&H) Do these experiments and record results clearly in the work sheets
Collins’ Worksheet C3b 6 (two sheets)
(H) Same as above but try to explain these:
Explain the very high melting points of Sodium chloride and magnesium oxide
Why solid ionic compounds do not conduct electricity
When a solid ionic compound is melted or dissolved in water it conducts electricity

53. Answers for the Higher part
There is a very strong attraction between the positive and negative ions in Sodium chloride and magnesium oxide. To melt these substances these strong attractive forces have to be broken by heating . This is why they have high belting points
Ions cannot move in solid . This is why a solid ionic compounds do not conduct electricity
When ionic compounds are melted or dissolved , the ions become free to move. so they conduct electricity

54. Higher only task
Describe the structure of sodium chloride and magnesium oxide

55. Describing structure of solid sodium chloride and magnesium chloride:
The are made of ………….. ionic lattices in which ………… ions e…………………. attarct ………….. ions.

56. Describing structure of solid sodium chloride and magnesium chloride:
The are made of giant ionic lattices in which positive ions electrostatically attarct negative ions.

57. Challenge! A book of data gives the following information for two
well known ionic compounds:
Compound
Melting point (°C)
Boiling point (°C)
sodium chloride
808
1465
magnesium oxide
2800
3600
sodium
chloride
magnesium
oxide
Na+
Which compound has the higher melting and boiling points?
Complete this table showing the charges on the ions.
From your answers in part (b), suggest why magnesium oxide has a higher melting and boiling point than sodium chloride.

58. Essential ideas
Ionic bonding is the e………… attraction between a …………… ion and a negative ion
Ionic bonding is mostly between …………….. and non-metals. Metals form the …………. ion and non-metals form ………… ions
Charged particles are called ………………
Li+ is formed by lithium atom ……………… an electron
Cl- atom is formed by …………….. an electron
Solid Sodium chloride and magnesium oxide have very ………….. melting points
Solid sodium chloride and magnesium oxide do not conduct ……………. as they do not contain freely moving ……….. when they are solids
When melted or ………………. solid sodium chloride and magnesium oxide conduct electricity

59. Essential ideas- answers
Ionic bonding is the electrostatic attraction between a positive ion and a negative ion
Ionic bonding is mostly between metals and
non-metals. Metals form the positive ion and non-metals form negative ions
Charged particles are called ions
Li+ is formed by lithium atom losing an electron
Cl- atom is formed by gaining an electron
Solid Sodium chloride and magnesium oxide have very high melting points
Solid sodium chloride and magnesium oxide do not conduct electricity as they do not contain freely moving ions when they are solids
When melted or dissolved solid sodium chloride and magnesium oxide conduct electricity

60. You should know these by now:
What is an ion?
Sodium chloride and magnesium oxide are examples of …………. Compounds and both have …………. melting points
Which one of the above ionic substances dissolves in water?
Why do they have very high melting points?
Why they do not conduct electricity when they are solids?
Why they conduct electricity when melted or dissolved in water?

61. Which of the following is not a sub-atomic particle?
Proton.
Isotope.
Neutron.
Electron.

62. The element Cobalt has a relative atomic mass of 59 and an atomic number of 27. Which of these is a true statement about each neutral cobalt atom?
It contains 59 neutrons.
It contains 27 electrons.
It contains 32 protons.
It contains equal numbers of neutrons and electrons.

63. contains more protons than neutrons.
The Periodic Table displays iron as shown below. This indicates that Fe atoms:
contain 56 neutrons.
contain 30 electrons.
contain 26 protons.
contains more protons than neutrons. 56 Fe 26

64. Which of the following is true: Both isotopes contain 35 protons.
Bromine consists of a mixture of two isotopes: Bromine-79 and Bromine-81
Which of the following is true:
Both isotopes contain 35 protons.
Bromine 79 contains 46 neutrons.
Bromine 81 contains 44 neutrons.
Bromine-81 is more reactive than bromine-79. 80 Br 35

65. Which answer best describes the shell arrangement of the electrons in a sodium atom?
2,8,1.
2,2,7.
2,8,8,3.
2,8,8,1. 23 Na 11

66. Which answer best describes the shell arrangement of the electrons in an oxygen atom?
2,8,6.
2,8,8.
2,8.
2,6. 16 O 8

67. Which of these elements will have electron shells that are either full or empty (i.e. not partially full)? 14 N 7 A 40 Ar 18 B 40 Ca 20 C 27 Al 13 D

68. Which answer best describes the shell arrangement of the electrons in an oxide ion O2-?
2,8,6.
2,8,8.
2,8.
2,6. 16 O 8