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Starter. What are the charges of the ions in these compounds? NaCl MgF 2 CaS Al 2 O 3 HCl HNO 3 H 2 SO 4 H 3 PO 4. Starter Answers. What are the charges of the ions in these compounds? NaCl Na + Cl - MgF 2 Mg 2+ F - CaS Ca 2+ S 2- Al 2 O 3 Al 3+ O 2- HCl H + Cl -

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  1. Starter • What are the charges of the ions in these compounds? • NaCl • MgF2 • CaS • Al2O3 • HCl • HNO3 • H2SO4 • H3PO4

  2. Starter Answers • What are the charges of the ions in these compounds? • NaCl Na+Cl- • MgF2 Mg2+ F- • CaS Ca2+ S2- • Al2O3 Al3+ O2- • HCl H+Cl- • HNO3 H+ NO3- • H2SO4 H+ SO42- • H3PO4 H+ PO43- • What is different about the second 4 compared to the first 4? (other than the fact they are acids)

  3. Starter Answers • What are the charges of the ions in these compounds? • NaCl Na+Cl- • MgF2 Mg2+ F- • CaS Ca2+ S2- • Al2O3 Al3+ O2- • HCl H+Cl- • HNO3 H+ NO3- • H2SO4 H+ SO42- • H3PO4 H+ PO43- • They only exist as separate ions in solution... We can start to think of atoms in covalently bonded molecules as having their own charges too... • ...They don’t have charges though... • ... They have oxidation states

  4. Ionic Compound Formulae

  5. Objectives Be able to... • Describe the basic structure of the periodic table in terms of blocks, groups, and periods • Recall and explain the charges of ions formed by members of s and p blocks • Recall the charges on more complex cations and anions and write formulae of compounds formed by them

  6. Specification...Where this comes from...

  7. How many electrons in the outer shells... • The atoms of group 1 elements? • The atoms of group 2 elements? • The atoms of group 3 elements? • The atoms of group 4 elements? • The atoms of group 5 elements? • The atoms of group 6 elements? • The atoms of group 7 elements? • The atoms of group 8/0 elements?

  8. How many electrons in the outer shells... • The atoms of group 1 elements? 1 • The atoms of group 2 elements? 2 • The atoms of group 3 elements? 3 • The atoms of group 4 elements? 4 • The atoms of group 5 elements? 5 • The atoms of group 6 elements? 6 • The atoms of group 7 elements? 7 • The atoms of group 8/0 elements? 8 or 0 • Get the picture??

  9. What do the members of the following groups want to do? • Group 1 • Group 2 • Group 3 • Group 5 • Group 6 • Group 7 • Group 8/0

  10. What do the members of the following groups want to do? • Group 1 – lose 1 electron • Group 2 – lose 2 electrons • Group 3 – lose 3 electrons • Group 5 – gain 3 electrons • Group 6 – gain 2 electrons • Group 7 – gain 1 electron • Group 8/0 – Nothing because they are happy just the way they are!

  11. Atoms that lose electrons have more protons than electrons and so have a positive charge. They are called positive ions or cations. Atoms that gain electrons have more electrons than protons and so have a negative charge. They are called negative ions or anions. Atoms and electron changes Atoms can obtain completely full outer electron shells by either gaining or losing electrons when they react with other atoms. When this happens, atoms become ions. Unlike atoms, ions have an electrical charge because they contain an unequal number of protons and electrons.

  12. The electron configuration of an atom gives information about how many electrons it must lose or gain to achieve a stable, noble gas configuration. Charges on ions When atoms form ions they obtain an outer electron shell that is either completely full or completely empty. • For atoms with a nearly empty outer shell, it takes less energy to lose electrons to have a full outer shell than it does to gain electrons. • For atoms with a nearly full outer shell, it takes less energy to gain electrons to have a full outer shell than it does to lose electrons.

  13. lithium atom = 2.1 ion = Li+ (not Li1+) ion = Mg2+ magnesium atom = 2.8.2 aluminium atom = 2.8.3 ion = Al3+ Positive ions 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 them to indicate how many electrons they have lost. This number is usually the same as the number of electronsin the atom’s outer shell. For example:

  14. Total charge = +1 Total charge = 0 + one electron is lost Na Na Electron arrangement: [2.8]+ (full outer shell) Sodium ion: Sodium atom: The sodium ion 11 protons = +11 11 protons = +11 10 electrons = -10 11 electrons = -11 Electron arrangement: 2.8.1 (partially full outer shell)

  15. Total charge = +2 Total charge = 0 2+ two electrons are lost Mg Mg Electron arrangement: [2.8]2+ (full outer shell) Magnesium ion: Magnesium atom: The magnesium ion 12 protons = +12 12 protons = +12 10 electrons = -10 12 electrons = -12 Electron arrangement: 2.8.2 (partially full outer shell)

  16. chlorine atom = 2.8.7 chloride ion = Cl- (not Cl1-) oxide ion = O2- oxygen atom = 2.6 nitrogen atom = 2.5 nitride ion = N3- Negative ions An atom that gains one or more electrons forms a negative ion. Non-metal atoms, such as chlorine, oxygen and nitrogen,form positive ions. Negative ions have a small ‘-’ symbol and a number by them to indicate how many electrons they have gained to fill their outer shell. For example: The name of the ion is slightly different to that of the atom – it ends ‘–ide’.

  17. Total charge = - 1 Total charge = 0 - one electron is gained F F Electron arrangement: [2.8]- (full outer shell) Fluoride ion: Fluorine atom: The fluoride ion 9 protons = +9 9 protons = +9 10 electrons = -10 9 electrons = -9 Electron arrangement: 2.7 (partially full outer shell)

  18. Total charge = - 2 Total charge = 0 2- two electrons are gained S S Electron arrangement: [2.8.8]2- (full outer shell) Sulfide ion: Sulfur atom: The sulfide ion 16 protons = +16 16 protons = +16 18 electrons = -18 16 electrons = -16 Electron arrangement: 2.8.6 (partially full outer shell)

  19. Building an ion

  20. Calculating ion charges What charges will the ions of these elements have? 2+ + 3- 1- 2+

  21. Metal Ion Example of compound Transition metal ions Some transition metals only make one type of ion.For example: • silver only forms Ag+ ions; • zinc only forms Zn2+ ions. However, most transition metals make more than one type of ion by losing different numbers of electrons. For example: Cu+ copper (I) oxide – Cu2O copper Cu2+ copper (II) oxide – CuO Fe2+ iron (II) chloride – FeCl2 iron Fe3+ iron (III) chloride – FeCl3

  22. Comparing electron configurations

  23. Comparing positive and negative ions

  24. A formula uses chemical symbols and numbers to show the ratio of atoms of each element present in the compound. Formulae of ionic compounds To work out the formula of an ionic compound, follow this procedure: 1. Write down the symbol for each atom. 2. Calculate the charge for each ion. 3 Balance the number of ions so the positive and negative charges equal zero. This gives a ratio of ions. 4. Write down the formula without the ion charges – the metal is always written first.

  25. Formula of sodium fluoride Na Fl Na+ Fl- 1 electron What is the formula of sodium fluoride? Na F 1- 1+ 1 sodium ion is needed for each fluoride ion 1 : 1 NaF

  26. Formula of aluminium bromide Br Br+ 1 electron for each atom Al Br Al3+ Br+ Br Br+ What is the formula of aluminium bromide? Al Br 1- 3+ 3 bromide ions are needed for each aluminium ion 1 : 3 AlBr3

  27. O O2- Al Al3+ 2 electrons for each atom O O2- Al3+ Al O O2- What is the formula of aluminium oxide? Formula of aluminium oxide Al O 2- 3+ 2 aluminium ions are needed for 3 oxide ions 2 : 3 Al2O3

  28. More ionic formulae metals non-metals Work out the formulae of all the possible ionic compounds from combinations of these metals and non-metals.

  29. More ionic formulae metals non-metals Work out the formulae of all the possible ionic compounds from combinations of these metals and non-metals. LiF CaF2 NaF MgF2 AlF3 KF Li2O CaO Na2O MgO Al2O3 K2O Li3N Ca3N2 Na3N Mg3N2 AlN K3N LiBr CaBr2 NaBr MgBr2 AlBr3 KBr Li2S CaS Na2S MgS Al2S3 K2S LiCl CaCl2 NaCl MgCl2 AlCl3 KCl

  30. Compound ions hydrogen-carbonate HCO3-1- Ionic compounds can contain ions consisting of groups of atoms rather than a single atom. These are compound ions. Ion Formula Charge Atoms present O H hydroxide OH- 1- S O O O O sulfate SO42- 2- N O O O nitrate NO3-1- C O O O carbonate CO32- 2- N H H H H ammonium NH4+ 1+ H C O O O

  31. More complicated formulae Working out the formulae for compounds containing compound ions is the same as for simple ionic compounds. The compound ion is treated as a single particle, not individual particles. 1. Write down the symbol for each atom. 2. Calculate the charge for each ion. 3 Balance the number of ions so the positive and negative charges equal zero. This gives a ratio of ions. 4. Write down the formula without the ion charges. If more than one compound ion is required, brackets must be put around the ion, before the number.

  32. More complicated formulae Determine the formulae of... Lithium nitrate Magnesium nitrate Aluminium hydroxide Ammonium sulfate Aluminium carbonate

  33. Formula of lithium nitrate What is the formula of lithium nitrate? Li NO3 1- 1+ 1 lithium ion is needed for each nitrate ion 1 : 1 LiNO3

  34. The brackets around NO3 indicate that the ‘2’ refers to a complete nitrate ion. Formula of magnesium nitrate What is the formula of magnesium nitrate? Mg NO3 1- 2+ 2 nitrate ions are needed for each magnesium ion 1 : 2 Mg(NO3)2

  35. Formula of sodium sulfate Although ‘Na’ contains 2 letters, it represents a single atom, so no brackets are required. What is the formula of sodium sulfate? Na SO4 2- 1+ 2 sodium ions are needed for each sulfate ion 2 : 1 Na2SO4

  36. Formula of aluminium hydroxide What is the formula of aluminium hydroxide? Al OH 1- 3+ 3 hydroxide ions are needed for each aluminium ion 1 : 3 Al(OH)3

  37. Formula of ammonium sulfate What is the formula of ammonium sulfate? NH4 SO4 2- 1+ 2 ammonium ions are needed for each sulfate ion 2 : 1 (NH4)2SO4

  38. Although ‘Al’ contains 2 letters, it represents a single atom, so no brackets are required. What is the formula of aluminium carbonate? Formula of aluminium carbonate Al CO3 2- 3+ 2 aluminium ions are needed for 3 carbonate ions 2 : 3 Al2(CO3)3

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