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© Boardworks Ltd 2003 CHEMICAL BONDING PART 1 IONIC BONDING.

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Presentation on theme: "© Boardworks Ltd 2003 CHEMICAL BONDING PART 1 IONIC BONDING."— Presentation transcript:

1 © Boardworks Ltd 2003 CHEMICAL BONDING PART 1 IONIC BONDING

2 © Boardworks Ltd 2003 Elements Elements are the simplest substances. There are about 100 different elements N S O C Fe K N N N N N N N N Each elements has just one particular type of atom that is different to the atoms in any other element Even in elements atoms usually join (bond) together. In some elements atoms bond to form small simple structures. In other elements atoms bond into giant structures with millions of atoms.

3 © Boardworks Ltd 2003 Compounds Compounds are formed when different elements chemically react together. In these reactions different types of atom become chemically bonded. Like elements some compounds have small simple structures with just a few atoms bonded together Other compounds have large, complex structures containing thousands or even millions of bonded atoms. O HH Water – a simple structure DNA – a large & complex structure

4 © Boardworks Ltd 2003 Compounds are not just mixtures Reacting is different to just mixing. veryThe physical and chemical properties of compounds are very different to their original elements. Carbon + oxygen Carbon dioxide COMPOUND ELEMENTS C OOCOO (black solid) (colourless gas, that supports combustion) (a colourless gas, that extinguishes fire)

5 © Boardworks Ltd 2003 Copy the Table and fill in the last column. SiO 2 Sand HgMercury Fe 2 O 3 Rust O2O2 Oxygen H2OH2OWater CuSO 4 Copper sulphate NiNickel NaClSodium chloride Element or compound FormulaName compound element compound element compound element compound Rust consists of iron combined with oxygen Activity

6 © Boardworks Ltd 2003 Bonding and atoms –Protons } These exist in –Neutrons } the nucleus. To understand bonding we must know a little about the atoms from which elements are made. Atoms consist of three types of particles that are even smaller than atoms: –Electrons } exist in layers (or shells) around the outside of the nucleus

7 © Boardworks Ltd 2003 No charge on element atoms Two of the three particles in atoms have an electrical charge. Protons +1 Neutrons 0 Electrons -1 BUT BUT atoms have equal numbers of protons and electrons. This means their overall charge = zero. Fluorine 9 protons9+ 9 electrons9- 10 neutrons0 Total Charge 0 19 F 9 For example 20 Ne 10 Neon Copy & Fill in the gaps ___ protons___ ___ electrons ___ ___neutrons___ Total Charge___

8 © Boardworks Ltd 2003 Noble Gases: full shells The electrons around the outside of atoms are arranged in layers called shells Each shell has a maximum number of electrons that it can hold. In noble gases the shells are completely full rather than partially full. During bonding other atoms try to attain the “full electron shell” structure of the noble gases. 1 st Shell: 2 electrons 2nd Shell: 8 electrons 3rd Shell: 8 electrons

9 © Boardworks Ltd 2003 Types of bonding Atoms can be joined together in 3 possible ways All three types involve changes in the electrons in the outermost electron shells of the atoms Ionic Bonding Metal and non-metal Covalent Bonding Non-metals only Metallic Bonding Metals only

10 © Boardworks Ltd 2003 IONIC BONDING

11 © Boardworks Ltd 2003 Most ionic compounds contain a metal and a non-metal. When metals react they lose outer shell electrons to leave a full electron shell. This produces a charged atom (ion) with a + charge. Lose 1 or more electrons Neutral atom n+n+ Positive ion When non-metals react with a metal they gain electrons to achieve a full electron shell. Gain 1 or more electrons Neutral atom n-n- Negative ion IONIC BONDING

12 © Boardworks Ltd 2003 opposites attract Opposites attract – lattices The oppositely charged ions are attracted into a lattice that gets bigger and bigger until it consists of millions of ions And ion, and ion, and ion!

13 © Boardworks Ltd 2003 Lattices are 3-Dimensional We have shown ions attracting and building 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.

14 © Boardworks Ltd 2003 Ions and electron structures Metals lose electrons to form positive(+) ions called cations. Non-metals gain electrons to form negative (–) ions called anions. n+n+ n-n- We know that the atoms lose or gain electrons to achieve full electron shells. To understand more about how ionic compounds form we must look at what is happening to the outer shell electrons.

15 © Boardworks Ltd 2003 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. Loses 1 electron Sodium 1+ ion (2.8.0) Sodium atom (2.8.1) This only happens if there is another atom able to accommodate the lost electron. Na Na+

16 © Boardworks Ltd 2003 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. Chlorine atom (2.8.7) Gains 1 electron (from sodium) Chlorine I - ion (2.8.8) Cl

17 © Boardworks Ltd 2003 Formation of Sodium Chloride- the overall process. Cl Na Cl Sodium loses its outer electron. Chlorine gains it. The result is both end up with full shells Two oppositely charged ions are formed, which attract. Millions of such pairs form a giant lattice

18 © Boardworks Ltd 2003 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

19 © Boardworks Ltd 2003 O Mg Magnesium atom Oxygen atom Bonding in Magnesium Oxide More than one electron may be transferred between atoms in ionic bonding. Mg2+ O Magnesium Oxide

20 © Boardworks Ltd 2003 Draw a simplified bonding diagram (omitting inner shells) for magnesium oxide. Mg O Magnesium atom Oxygen atom Mg2+ O2- Magnesium Oxide

21 © Boardworks Ltd 2003 Sodium Fluoride Sodium atom Fluorine atom Copy the diagram and draw another box showing the electron configuration in sodium fluoride. Na+ 2.8 F Na F-

22 © Boardworks Ltd 2003 Bonding in Lithium Oxide The bonding in lithium oxide is more complicated in that there are different numbers of each atom. Li O Li+ O2-

23 © Boardworks Ltd 2003 Bonding in Lithium Nitride The bonding in lithium nitride similarly involves different numbers of each atom. N Li Li+ N 3- Li

24 © Boardworks Ltd 2003 Bonding in Aluminium Fluoride In aluminium fluoride it is the non-metal atoms that we need more of. F F F Al F F F

25 © Boardworks Ltd 2003 Following the previously shown slides draw bonding diagrams for the compounds formed from the following atoms: 1.Lithium (2.1) and fluorine (2.7) 2.Sodium (2.8.1) and sulphur (2.8.6) 3.Magnesium (2.8.2) and sulphur (2.8.6) 4.Magnesium (2.8.2) and fluorine (2.7) 5.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 Activity

26 © Boardworks Ltd electrons Electrons Lost = Electrons Gained Both sodium chloride and magnesium oxide are simple ionic compounds. In both cases the metal and non-metal need to lose or gain the same number of electrons respectively. Na Cl 1 electron Na + Cl - O Mg O 2- Mg 2+ This is not always the case.

27 © Boardworks Ltd 2003 Different numbers of electrons Consider the reaction of sodium with oxygen. –Sodium (2.8.1) needs to lose 1 electron. –Oxygen (2.6) needs to gain 2 electrons This can only happen if there are two sodium ions formed for every one oxygen ion formed. The formula will be Na 2 O. Na O Na + O 2- Na + 1 electron per sodium

28 © Boardworks Ltd 2003 Consider the reaction of magnesium with chlorine. –Magnesium (2.8.2) needs to lose 2 electron. –Chlorine (2.8.7) needs to gain 1 electrons We need 2 chlorines for every one magnesium. The formula will be MgCl 2 Cl Mg Cl Mg 2+ Cl - 2 electrons Different numbers of electrons

29 © Boardworks Ltd 2003 Charges on ions When atoms form ions they aim to attain electron shells that are either completely full or completely empty. If we know the electron configuration of an atom we can usually work out how many electrons it must lose or gain to achieve a noble gas configuration. This will tell us the charge on its ion.

30 © Boardworks Ltd 2003 Charges and Metal ions Metals usually lose electrons to empty this outer shell. The number of electrons in the outer shell is usually equal to the group number in the Periodic Table. For example, Mg  Mg 2+ Al  Al 3+ Li 2.1  Li +

31 © Boardworks Ltd 2003 Charges and non-metal ions Outer shells with 5 or more electrons usually gain electrons to fill up the outer shell. For example, Oxygen (2.6) gains 2 electrons to form O 2- Chlorine (2.8.7) gains 1 electron to form Cl - Cl O 2.6  2.8 O  O  Cl  Cl -

32 © Boardworks Ltd 2003 Copy out and fill in the Table below showing what charge ions will be formed from the elements listed. H He Li Na K Be ScTi Mg VCrMnFeCoNiCuZnGaGeSeBrCaKr AlP NO SCl FNe ArSi BC As Mg C Cl K Na Charge Outer electrons NeBrOAlKCaClNLi Symbol Activity

33 © Boardworks Ltd 2003 The formulae of ionic compounds This is most quickly done in 5 stages. Remember the total + and – charges must =zero For example, For example, the formula of calcium bromide. 1.Symbols:CaBr 2.Charge on ions Need more ofBr 4.Ratio of ions12 CaBr 2 5.Formula CaBr 2 Br Ca Br Ca 2+ Br - 2 electrons

34 © Boardworks Ltd 2003 For example, the formula of aluminium bromide. 1.Symbols:AlBr 2.Charge on ions Need more ofBr 4.Ratio of ions13 AlBr 3 5.Formula AlBr 3 Br Al Br 3 electrons Al 3+ Br - The formulae of ionic compounds

35 © Boardworks Ltd 2003 For example, the formula of aluminium oxide. 1.Symbols : AlO 2.Charge on ions Need more ofO 4.Ratio of ions23 (to give 6 e - ) Al 2 O 3 5.Formula Al 2 O 3 O Al O O 2e - Al 3+ O 2- Al 3+ The formulae of ionic compounds

36 © Boardworks Ltd 2003 all Using the method shown on the last few slides, work out the formula of all the ionic compounds that you can make from combinations of the metals and non-metals shown below: Metals: Li Ca Na Mg Al K Non-Metals: F O N Br S Cl Activity

37 © Boardworks Ltd 2003 More Complicated Formulae Ionic compounds may contain ions consisting of groups of atoms rather than a single atom. Here are some more complicated ions you may come across. Atoms presentChargeFormulaIon CO 3 2- OH - NH 4 + SO 4 2- NO 3 - carbonate hydroxide ammonium sulphate nitrate NOOO O SOOO N HHHH O H C O O O

38 © Boardworks Ltd Symbols :LiNO Charge on ions Need more of neither 4.Ratio of ions11 LiNO 3 5.Formula LiNO 3 When working out formula you simply treat the entire group of atoms as though it were a single atom. The only difficulty is to do with how we write down the final answer. For example, what is the formula of lithium nitrate? More Complicated Formulae

39 © Boardworks Ltd Symbols :MgNO Charge on ions Need more of NO Ratio of ions12 Mg(NO 3 5.Formula Mg(NO 3 ) 2 What is the formula of magnesium nitrate? The brackets around the NO 3 - ion show that the 2 refers to two complete NO 3 - ions. It represents a total of 2 nitrogens and 6 oxygens with each magnesium ion. More Complicated Formulae

40 © Boardworks Ltd 2003 What is the formula of sodium sulphate? 1.Symbols :Na + SO Charge on ions Need more of Na + 4.Ratio of ions21 Na 2 SO 4 5.Formula Na 2 SO 4 No brackets here as only one SO 4 2- ion needed. Note although Na contains 2 letters it only represents a single atom – so no brackets! More Complicated Formulae

41 © Boardworks Ltd Symbols : 2.Charge on ions 3.Need more of 4.Ratio of ions 5.Formula Again we need brackets as 3 complete OH - ions are needed meaning that for each aluminium there are 3 oxygens and 3 hydrogens. Al 3+ OH OH Al(OH) 3 Write down how to work out the formula of aluminium hydroxide.

42 © Boardworks Ltd Symbols : 2.Charge on ions 3.Need more of 4.Ratio of ions 5.Formula Again we need brackets as 2 complete NH 4 + ions are needed meaning that for each sulphate ion there are 2 nitrogen and 8 hydrogens. NH 4 + SO (NH 4 ) 2 SO 4 NH 4 + Write down how to work out the formula of ammonium sulphate.

43 © Boardworks Ltd Symbols : 2.Charge on ions 3.Need more of 4.Ratio of ions 5.Formula No brackets for Al as only one atom even though it’s 2 letters. We do need brackets around the SO 4 to show it is 3 complete sulphate ions. Al 3+ SO Al 2 (SO 4 ) 3 Need to get total charge =6 Write down how to work out the formula of aluminium sulphate.

44 © Boardworks Ltd 2003 Formed when a _____ and non-metal react. Metals ___ electrons to empty their outer electron shell. Non-metals _____ electrons to fill their outer electron shell. The ratio of metal ions to non-metal ions will depend upon the number of ________ lost and gained. The ions formed join up into giant _____. Copy this choosing words from below to fill the gaps. loselattices electronsgainmetal lose gain electrons lattices.

45 © Boardworks Ltd 2003 Which of the following will have ionic bonding? A. Copper chloride B. Iron C. Brass D. Sulphur dioxide

46 © Boardworks Ltd 2003 NOT Which of the following is NOT true of ionic bonding? A. Metal ions have a + charge B. Non-metal ions have a - charge C. They form a 2 dimensional lattice D. They have giant structures

47 © Boardworks Ltd 2003 Which of the following is true about the oxide ion? A.Formed by oxygen atoms losing 2 electrons. B.Oxygen ions have an empty second shell C.Exist in pairs D.Have a 2- charge 16 O 8

48 © Boardworks Ltd 2003 Which of the following is true about the sodium ion? A.Has a 2,8,1 electron arrangement B.Formed by sodium atoms gaining 1 electron. C.Sodium ions have an empty second shell D.Have a 1+ charge 23 Na 11

49 © Boardworks Ltd 2003 What formula compound will be formed from Mn 4+ and O 2- ions? A. Mn 2 O 4 B. MnO 2 C. Mn 2 O D. MnO 4

50 © Boardworks Ltd 2003 What formula compound will be formed from Ga 3+ and SO 4 2- ions? A. Ga 2 (SO 4 ) 3 B. Ga 3 (SO 4 ) 2 C. Ga 2 S 3 O 12 D. Ga (SO 4 ) 3


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