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Understanding Chemical Bonding and Ionic Bonds

Learn about elements, compounds, atoms, and ionic bonding. Discover how atoms combine to form compounds through the exchange of electrons, leading to the creation of ionic compounds. Explore the structure of ions and the attraction between positively and negatively charged ions.

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Understanding Chemical Bonding and Ionic Bonds

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  1. CHEMICAL BONDINGPART 1IONIC BONDING

  2. Elements are the simplest substances. There are about 100 different elements S Fe N O C K N N N N N N N N Elements • 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. 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. H H O Water – a simple structure DNA – a large & complex structure Compounds

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

  5. Activity Copy the Table and fill in the last column. Rust consists of iron combined with oxygen Name Formula Element or compound Sodium chloride NaCl compound Nickel Ni element Copper sulphate CuSO4 compound Water H2O compound Oxygen O2 element Rust Fe2O3 compound Mercury Hg element Sand SiO2 compound

  6. Protons } These exist in Neutrons } the nucleus. Bonding and atoms 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. Two of the three particles in atoms have an electrical charge. Protons +1 Neutrons 0 Electrons -1 19 F 9 20 Ne 10 Fluorine 9 protons 9+ 9 electrons 9- 10 neutrons 0 Total Charge 0 Neon Copy & Fill in the gaps ___ protons ___ ___ electrons ___ ___neutrons ___ Total Charge ___ No charge on element atoms BUT atoms have equal numbers of protons and electrons. This means their overall charge = zero. For example 10+ 10 10 10- 0 10 0

  8. The electrons around the outside of atoms are arranged in layers called shells 1st Shell: 2 electrons 2nd Shell: 8 electrons 3rd Shell: 8 electrons Noble Gases: full 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.

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

  10. IONIC BONDING

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

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

  13. We have shown ions attracting and building into a 2 dimensional sheet. + + + + + + - - - - - - - - - - - - + + + + + + + + + + + + - - - - - - - - - - + + + + - - - - + + + + + + - - - - - - + + + + + + + + + + - - - - + + + + - - - - + + + + - - - - Lattices are 3-Dimensional 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. Metals lose electrons to form positive(+) ions called cations. n+ n- Ions and electron structures Non-metals gain electrons to form negative (–) ions called anions. • 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. Sodium has 1 electron in its outer shell. Loses 1 electron Na+ Na Formation of sodium chloride1. Formation of sodium ions If it loses this it will have no partially filled shells. 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.

  16. Chlorine has 7 electrons in its outer shell. Cl Gains1 electron (from sodium) Cl Formation of sodium chloride 2.Formation of Chloride ions 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) Chlorine I - ion (2.8.8)

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

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

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

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

  21. Copy the diagram and draw another box showing the electron configuration in sodium fluoride. Na F Sodium Fluoride 2.7 2.8.1. Sodium atom Fluorineatom Na+ F- 2.8 2.8

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

  23. The bonding in lithium nitride similarly involves different numbers of each atom. Li Li Li Li N N3- Li+ Li+ Bonding in Lithium Nitride

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

  25. 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) Activity Remember that the total number of electrons lost by the metal must equal the total number of electrons gained by the non-metal

  26. 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 Cl- Na+ 1 electron O2- Mg2+ O Mg 2 electrons Electrons Lost = Electrons Gained This is not always the case.

  27. 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. Na+ Na O O2- 1 electron per sodium Na+ Na Different numbers of electrons The formula will be Na2O.

  28. 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. Cl Cl- Mg Mg2+ Cl- Cl 2 electrons Different numbers of electrons The formula will be MgCl2

  29. 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. Charges on ions

  30. 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, Li 2.8.3  Al3+ 2.8.2 Mg2+ Mg Al 2.1Li+ Charges and Metal ions

  31. 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 O2- Chlorine (2.8.7)gains 1 electron to form Cl- Cl O Charges and non-metal ions 2.8.7 2.8.8Cl  Cl- 2.62.8 O O2-

  32. Copy out and fill in the Table below showing what charge ions will be formed from the elements listed. Activity H He C Li Be B C N O F Ne Na Mg Al Si P S Cl Cl Ar Mg K K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Symbol Li N Cl Ca K Al O Br Na Ne Outer electrons 1 5 7 1 3 6 2 7 1 8 Charge 1+ 2+ 1+ 3+ 0 3- 1- 2- 1- 1+

  33. This is most quickly done in 5 stages. Remember the total + and – charges must =zero For example, the formula of calcium bromide. Symbols: Ca Br Charge on ions 2+ 1- Need more of Br Ratio of ions 1 2 Formula CaBr2 Br Br- Ca Ca2+ Br- Br 2 electrons The formulae of ionic compounds

  34. For example, the formula of aluminium bromide. Symbols: Al Br Charge on ions 3+ 1- Need more of Br Ratio of ions 1 3 Formula AlBr3 The formulae of ionic compounds Br- Br Br- Al3+ Al Br Br- Br 3 electrons

  35. For example, the formula of aluminium oxide. Symbols: AlO Charge on ions 3+ 2- Need more of O Ratio of ions 2 3 (to give 6 e-) Formula Al2O3 The formulae of ionic compounds O2- O 2e- Al Al3+ O2- 2e- O Al Al3+ O2- O 2e-

  36. 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: Activity • Metals: Li Ca Na Mg Al K • Non-Metals: F O N Br S Cl

  37. 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. Ion Formula Charge Atoms present nitrate NO3- 1- sulphate SO42- 2- N O O O ammonium NH4+ 1+ O S O O O hydroxide OH- 1- N H H H H carbonate CO32- 2- H O O O O C More Complicated Formulae

  38. 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 • Symbols: Li NO3- • Charge on ions 1+ 1- • Need more of neither • Ratio of ions 1 1 • Formula LiNO3

  39. What is the formula of magnesium nitrate? More Complicated Formulae • Symbols: Mg NO3- • Charge on ions 2+ 1- • Need more of NO3- • Ratio of ions 1 2 • Formula Mg(NO3)2 • The brackets around the NO3- ion show that the 2 refers to two complete NO3- ions. • It represents a total of 2 nitrogens and 6 oxygens with each magnesium ion.

  40. What is the formula of sodium sulphate? More Complicated Formulae • Symbols: Na+SO42- • Charge on ions 1+ 2- • Need more of Na+ • Ratio of ions 2 1 • Formula Na2SO4 • No brackets here as only one SO42- ion needed. • Note although Na contains 2 letters it only represents a single atom – so no brackets!

  41. Write down how to work out the formula of aluminium hydroxide. • Symbols: • Charge on ions • Need more of • Ratio of ions • Formula Al3+ OH- 3+ 1- OH- 1 3 Al(OH)3 Again we need brackets as 3 complete OH- ions are needed meaning that for each aluminium there are 3 oxygens and 3 hydrogens.

  42. Write down how to work out the formula of ammonium sulphate. • Symbols: • Charge on ions • Need more of • Ratio of ions • Formula NH4+ SO42- 1+ 2- NH4+ 2 1 (NH4)2SO4 Again we need brackets as 2 complete NH4+ ions are needed meaning that for each sulphate ion there are 2 nitrogen and 8 hydrogens.

  43. Write down how to work out the formula of aluminium sulphate. • Symbols: • Charge on ions • Need more of • Ratio of ions • Formula SO42- Al3+ 2- 3+ Need to get total charge =6 2 3 Al2(SO4)3 No brackets for Al as only one atom even though it’s 2 letters. We do need brackets around the SO4 to show it is 3 complete sulphate ions.

  44. 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. metal lose gain electrons lattices.

  45. Which of the following will have ionic bonding? Copper chloride Iron Brass Sulphur dioxide

  46. Which of the following is NOT true of ionic bonding? Metal ions have a + charge Non-metal ions have a - charge They form a 2 dimensional lattice They have giant structures

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

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

  49. What formula compound will be formed from Mn4+ and O2- ions? Mn2O4 MnO2 Mn2O MnO4

  50. What formula compound will be formed from Ga3+ and SO42- ions? Ga2(SO4)3 Ga3(SO4)2 Ga2S3O12 Ga(SO4)3

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