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Boardworks GCSE Additional Science: Chemistry Ionic Bonding

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1 Boardworks GCSE Additional Science: Chemistry Ionic Bonding

2 Boardworks GCSE Additional Science: Chemistry Ionic Bonding

3 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
What are bonds? Boardworks GCSE Additional Science: Chemistry Ionic Bonding Elements are the simplest substances that exist on Earth. Each element is made up of just one type of atom, usually joined to other atoms of the same element by bonds. This forms molecules such as chlorine (Cl2). Compounds are formed when different elements chemically react and form bonds with each other. Some compounds, like water (H20), have small, simple structures with just a few atoms bonded together. Others compounds, like DNA, have large, complex structures containing thousands or even millions of bonded atoms.

4 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
Why do atoms form bonds? Boardworks GCSE Additional Science: Chemistry Ionic Bonding Bonds involve the electrons in the outer shells of atoms. Each shell has a maximum number of electrons that it can hold. Electrons fill the shells nearest the nucleus first. 1st shell holds a maximum of 2 electrons 2nd shell holds a maximum of 8 electrons 3rd shell holds a maximum of 8 electrons Filled electron shells are very stable.

5 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
Why do atoms form bonds? Boardworks GCSE Additional Science: Chemistry Ionic Bonding The atoms of noble gases have completely full outer shells and so are stable. This makes the noble gases very unreactive and so they do not usually form bonds. The atoms of other elements have incomplete outer electron shells and so are unstable. By forming bonds, the atoms of these elements are able to have filled outer shells and become stable.

6 What are the types of bonding?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Different types of bonds are formed depending on the types of atoms involved: ionic bonding – occurs between metal and non-metal atoms. covalent bonding – occurs between non-metals atoms only. metallic bonding – occurs between metal atoms only. Teacher notes See the GCSE Science chemistry ‘Metals and Alloys’ presentation for more information on metallic bonding. See the GCSE Additional Science chemistry ‘Covalent Bonding’ presentation for more information about covalent bonding. All bonds involve electrons and all bonding involve changes to the number of electrons in the outer shells of atoms. How do you think electrons are involved in ionic bonding?

7 Boardworks GCSE Additional Science: Chemistry Ionic Bonding

8 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
From atoms to ions Boardworks GCSE Additional Science: Chemistry Ionic Bonding How can reactive metal atoms become stable positive ions? Teacher notes This illustration contains representations of how metal atoms are unstable until they lose electrons when they become stable positive ions. It can be used as an introduction to the topic. There are several discussion points relating to the topic: Angry looking metal atoms Until atoms donate electrons to non-metals atoms, they are unstable and reactive. Self help books On the topic of donating and becoming positive – metal atoms that donate electrons will become positive and more stable and therefore ‘happier’. No drinking sign because the metal atoms are very reactive and would react readily with water.

9 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
How do atoms form ions? Boardworks GCSE Additional Science: Chemistry Ionic Bonding An ion is an atom or group of atoms that has an electrical charge, either positive and negative. Atoms have an equal number of protons and electrons and so do not have an overall charge. Atoms with incomplete outer electron shells are unstable. By either gaining or losing electrons, atoms can obtain full outer electron shells and become stable. When this happens, atoms have an unequal number of protons and electrons and so have an overall charge. This is how atoms become ions. How does an atom become a positive or negative ion?

10 Positive and negative ions?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding An atom that loses electrons has more protons than electrons and so has a positive overall charge. This is called a positive ion. An atom that gains electrons has more electrons than protons and so has a negative overall charge. This is called a negative ion. The electron configuration of an atom shows how many electrons it must lose or gain to have a filled outer shell. Atoms with a nearly empty outer shell, will lose electrons to obtain a full outer shell. Atoms with a nearly full outer shell, will gain electrons to obtain a full outer shell.

11 How do atoms form positive ions?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding An atom that loses one or more electrons forms a positive ion. Metal atoms, such as sodium, magnesium and iron, form positive ions. Positive ions have a small ‘+’ symbol and a number by this to indicate how many electrons have been lost. This number is usually the same as the number of electrons in the atom’s outer shell. For example: Teacher notes It should be pointed out that the lithium ion is represented by Li+ not Li1+. lithium ion [ 2 ] lithium atom 2.1 aluminium atom aluminium ion [ 2.8 ] magnesium atom magnesium ion [ 2.8 ] = Mg2+ = Li+ = Al3+

12 How is a sodium ion formed?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding 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)

13 How is a magnesium ion formed?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding 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)

14 How do atoms form negative ions?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding An atom that gains one or more electrons forms a negative ion. Non-metal atoms, such as chlorine, oxygen and nitrogen, form negative ions. Negative ions have a small ‘-’ symbol and a number by this to indicate how many electrons have been gained to fill their outer shell. For example: chlorine atom chloride ion [ ] = Cl- oxygen atom oxide ion [ 2 ] nitrogen atom nitride ion [ 2 ] 2.8.7 2.6 2.5 = N3- = O2- Teacher notes It should be pointed out that the chloride ion is represented by Cl- not Cl1- The name of the ion is slightly different to the atom’s name.

15 How is a fluoride ion formed?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding 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)

16 How is a sulfide ion formed?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding 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)

17 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
Building an ion Boardworks GCSE Additional Science: Chemistry Ionic Bonding Teacher notes This activity could be used to check students’ understanding of electron arrangement and how this changes during the formation of ions. It will also check their understanding of the charges on ions.

18 Calculating ion charges
Boardworks GCSE Additional Science: Chemistry Ionic Bonding What is the charge on the ion of each element? Element calcium hydrogen phosphorus fluorine beryllium Electron shells 1 2.8.5 2.7 2.2 Charge on ion +2 +1 -3 -1 +2

19 Electron configuration of ions
Boardworks GCSE Additional Science: Chemistry Ionic Bonding When different elements gain or lose electrons to complete their outer electron shell, they can create ions that have the same electron configuration. For example, oxygen and fluorine both gain electrons to become negative ions. The resulting ions have the same electron configuration: 2- O F - The number of protons and neutrons however, remain different for each element. This means that each ion has different properties.

20 Comparing electron configurations
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Teacher notes This matching activity could be used as a plenary exercise to check students’ ability to understand that different elements can have the same electron configuration when they become ions. It will also check their understanding of electron configuration of some of the elements and how this changes when they become ions. This activity will probably only be suitable for higher-level students.

21 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
What is a compound ion? Boardworks GCSE Additional Science: Chemistry Ionic Bonding 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

22 Comparing positive and negative ions
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Teacher notes This drag and drop activity provides the opportunity for informal assessment of students’ understanding of the differences between positive and negative ions. Appropriately coloured voting cards could be used with this activity to increase class participation.

23 Boardworks GCSE Additional Science: Chemistry Ionic Bonding

24 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
Ions and attraction Boardworks GCSE Additional Science: Chemistry Ionic Bonding Why do some ions attract while others repel? Teacher notes This illustration contains representations of ions attracting and repelling each other. It can be used as an introduction to the topic. There are several discussion points relating to the topic: The attraction of positive sodium and negative chlorine This is shown by the ‘clinch’ on the film poster, and by the couple with their arms around each other on the red carpet. It is also shown by the quote from a film reviewer discussing the ‘attraction of Sodium and Chlorine’ Sean Sodium is represented as ‘positive’ by the following: There is the Sean Sodium is described as being ‘positively fabulous’ On Sean Sodium’s bow tie there are small positive symbols. Clara Chlorine is represented as ‘negative’ by the following: On Clara Chlorine’s dress there are small negative symbols. Opposites attract and like repels Couples in the crowd are different – heights and sizes. People in the crowd who are very similar are shown not getting along and even ‘repelling’ each other.

25 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
What is ionic bonding? Boardworks GCSE Additional Science: Chemistry Ionic Bonding Compounds that contain ions are called ionic compounds. These compounds are usually formed by a reaction between a metal and a non-metal. Why do these substances react together and form bonds? The metal and non-metal atoms have incomplete outer electron shells and so are unstable. Electrons are transferred from each metal atom to each non-metal atom. The metal and the non-metal atoms form ions with completely full outer shells and become stable. The positive and negative ions are strongly attracted to each other. This electrostatic attraction is called ionic bonding.

26 How are ionic bonds formed?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Sodium chloride is an ionic compound formed by the reaction between the metal sodium and the non-metal chlorine. + Na Sodium has 1 electron in its outer shell. Na By losing this electron, it has a filled outer shell and forms a positive ion. 2.8.1 [2.8]+ Chlorine has 7 electrons in its outer shell. - Cl Cl By gaining an electron from sodium, it has a filled outer shell and forms a negative ion. 2.8.7 [2.8.8]-

27 How are ionic bonds formed?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding The positive sodium ions and the negative chloride ions are strongly attracted to each other. - Cl Na + It is this electrostatic attraction that forms ionic bonds in sodium chloride and other ionic compounds.

28 Formation of an ionic bond
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Teacher notes This two part interactive animation shows how bonding occurs in two compounds – sodium chloride and magnesium oxide. It shows how the ions are formed and which electrons are transferred and how this leads to the formation of the ionic lattices.

29 Ions and ionic bonding – summary
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Teacher notes This completing sentences activity could be used as a plenary or revision exercise on ions and ionic bonding. Students could be asked to write down the missing words in their books and the activity could be concluded by the completion on the IWB.

30 Boardworks GCSE Additional Science: Chemistry Ionic Bonding

31 What is the ratio of ions?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Sodium chloride (NaCl) and magnesium oxide (MgO) are simple ionic compounds. In each compound, the metal needs to lose the same number of electrons that the non-metal needs to gain. Na 1 electron Cl Na+ Cl- 2 electrons Mg O Mg2+ O2- Both compounds have a 1:1 ratio of metal ions to non-metal ions, which is shown by the formula of each compound.

32 What is the ratio of ions in sodium oxide?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding What is the ratio of ions needed to make sodium oxide? Sodium (2.8.1) needs to lose 1 electron to form a sodium ion but oxygen (2.6) must gain 2 electrons to form an oxide ion . Na Na+ 1 electron from each Na atom O2- O Na+ Na Two sodium atoms are required for each oxygen atom and so the ratio of sodium ions to oxide ions is 2:1. From this ratio, the formula of sodium oxide is Na2O.

33 What is the ratio of ions in magnesium chloride?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding What is the ratio of ions needed for magnesium chloride? Magnesium (2.8.2) needs to lose 2 electrons to form a magnesium ion but chlorine (2.8.7) needs to gain 1 electron to form an chloride ion. Cl Cl- 1 electron for each Cl atom Mg2+ Mg Cl- Cl Two chlorine atoms are required for each magnesium atom and so the ratio of magnesium ions to chloride ions is 1:2. From this ratio, the formula of magnesium chloride is MgCl2.

34 How to write the formula of an ionic compound
Boardworks GCSE Additional Science: Chemistry Ionic Bonding The formula of a compound uses chemical symbols and numbers to show the ratio of atoms of each element present. To work out the formula of an ionic compound: 1. Write down the symbol for each element – the metal is always written first. 2. Calculate the charge for each type of ion. 3. Balance the number of ions so that the positive and negative charges are balanced and equal zero. This gives the ratio of ions. 4. Use the ratio to write down the formula of the ionic compound.

35 Formula of aluminium bromide
Boardworks GCSE Additional Science: Chemistry Ionic Bonding What is the formula of aluminium bromide? Symbol Al Br Ion charge +3 -1 Balance the number of ions 3 bromide ions are needed for each aluminium ion Ratio of ions 1 : 3 Formula AlBr3 Br Br- 1 electron for each bromine atom Al Br Al3+ Br- Br Br-

36 Formula of aluminium oxide
Boardworks GCSE Additional Science: Chemistry Ionic Bonding What is the formula of aluminium oxide? Symbol Al O Ion charge +3 -2 Balance the number of ions 2 aluminium ions are needed for 3 oxide ions Ratio of ions 2 : 3 Formula Al2O3 2 electrons for each oxygen atom O O2- Al Al3+ O O2- Al3+ Al O O2-

37 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
More ionic formulae Boardworks GCSE Additional Science: Chemistry Ionic Bonding What are the formulae of all the possible ionic compounds from combinations of these metals and non-metals. metals non-metals Li Ca Na Mg Al K F LiF CaF2 NaF MgF2 AlF3 KF O Li2O CaO Na2O MgO Al2O3 K2O N Li3N Ca3N2 Na3N Mg3N2 AlN K3N Br LiBr CaBr2 NaBr MgBr2 AlBr3 KBr S Li2S CaS Na2S MgS Al2S3 K2S Cl LiCl CaCl2 NaCl MgCl2 AlCl3 KCl

38 What is the ionic formula?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Teacher notes This drag and drop activity could be used as a plenary exercise to check students’ ability to work out the formulae of ionic compounds. Class voting or the use of coloured traffic light cards could be make this a whole-class exercise.

39 Boardworks GCSE Additional Science: Chemistry Ionic Bonding

40 What is an ionic lattice?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding In an ionic compound, millions and millions of ions are packed together in a regular cubic arrangement, joined by ionic bonds. This forms a giant 3D structure called an ionic lattice. The ionic lattice will continue to build in this way until there are no more ions left to add. The structure of the ionic lattice affects the properties of the ionic compound.

41 Why do ionic compounds form crystals?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Ionic compounds such as sodium chloride, form crystals, with a cubic shape. This is due to the structure of the ionic lattice. Teacher notes Photo credit: Andrew Syred/Science Photo Library. The image is a coloured scanning electron micrograph (SEM) of common salt, sodium chloride, recrystallised from distilled water.  The salt crystal is built up from a cubic lattice of sodium and chloride ions. In the absence of impurities the exact cubic crystal form is produced. This micrograph shows that in practice this basic cube is usually disrupted by dislocations; these give rise to crystals with a variety of shapes, although they all retain the basic cubic symmetry. Magnification: x280 at 5x7cm size. x975 at 10x8‘. All ionic compounds form lattices and crystals when solid.

42 Heating ionic compounds
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Why are ionic compounds solid at room temperature and have high melting points and boiling points? Ion charges Melting point (oC) Boiling point (oC) Compound sodium chloride 1+ and 1- 801 1,413 magnesium oxide 2+ and 2- 2,852 3,600 strong ionic bonds hold ions together Ionic bonds are strong and a lot of heat is needed to break them. Larger ionic charges produce stronger ionic bonds and so much more heat is required to break the ionic bonds in magnesium oxide than in sodium chloride.

43 Do ionic compounds conduct electricity?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Teacher notes This virtual experiment illustrates which substances, and in what state conduct electricity and why. It could be used as a precursor to running the practical in the lab, or as a revision exercise. See also the GCSE Science chemistry ‘Metals and Alloys’ presentation for more information on metallic bonding. See the GCSE Additional Science chemistry ‘Covalent Bonding’ presentation for more information about covalent bonding.

44 How can ionic compounds conduct electricity?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding As solids, ionic compounds cannot conduct electricity because their ions are bonded together in the lattice. ions in solid state cannot move When liquid (molten), the ions can break free of the lattice and are able to move. The ions are charged particles and so can carry an electric current. ions in molten state can move and conduct electricity Ionic compounds are usually soluble in water because water molecules have a slight electrical charge and so can attract the ions away from the lattice. When dissolved, the ions are free to move and can carry an electric current.

45 Why are ionic compounds brittle?
Boardworks GCSE Additional Science: Chemistry Ionic Bonding Ionic compounds are brittle – they shatter when they are hit. Ionic bonds are strong, so why does this happen? force repulsion When the lattice is hit, a layer of ions is shifted so that ions with the same charges are lined up together. These like charges repel each other and so split the ionic lattice causing it to shatter.

46 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
True or false? Boardworks GCSE Additional Science: Chemistry Ionic Bonding Teacher notes This true-or-false activity could be used as a plenary or revision exercise on the properties of ionic compounds, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.

47 Boardworks GCSE Additional Science: Chemistry Ionic Bonding

48 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
Glossary Boardworks GCSE Additional Science: Chemistry Ionic Bonding  bond – A strong force that joins atoms or ions together in molecules and giant lattices.  compound ion – An ion made up of a group of atoms, rather than one single atom.  ionic bond – The electrostatic force of attraction between oppositely charged ions.  ionic compound – A compound made up of ions.  ionic lattice – A giant 3D structure of closely packed, oppositely-charged ions.  negative ion – An atom or group of atoms that has gained electrons and so has a negative charge.  noble gas – An element that has a full outer electron shell and so is very stable and unreactive.  positive ion – An atom or group of atoms that has lost electrons and so has a positive charge.

49 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
Anagrams Boardworks GCSE Additional Science: Chemistry Ionic Bonding

50 Boardworks GCSE Additional Science: Chemistry Ionic Bonding
Multiple-choice quiz Boardworks GCSE Additional Science: Chemistry Ionic Bonding Teacher notes This multiple-choice quiz could be used as a plenary activity to assess students’ understanding of ionic bonding. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.


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