_archIons ^0 Ionic Bonding PPT copy copy copy.pptx

Ionic

1. Ions & Ionic Bonding

2. Work out the electronic structure of the following, using the 2,8,8,18 method. Lithium Bromine Argon Vanadium Zinc Aluminium 2,8,8,17 2,1 2,8,8,5 2,8,8 2,8,8,12 2,8,3

3. Learning Outcomes 1. What How and why ions are formed and how they make bonds 2. How Working out ions and the bonding between them 3. Why To know how compounds are made.

4. How can reactive atoms become stable?

5. What is an Ion? An ion is an atom or group of atoms that has an electrical charge, either positive and negative. Atoms with incomplete outer electron shells are unstable. By either gaining or losing electrons, atoms can obtain full outer electron shells and become stable.

6. 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 .

7. Ions An ion is formed when an atom gains or loses electrons and becomes 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) + - + The electron is negatively charged The proton is positively charged +

8. Simple Ions Cations Sodium – Na + Magnesium – Mg 2+ Iron – Fe 3+ Copper – Cu 2+ Anions Chloride – Cl - Sulphate – SO 4 2- Carbonate – CO 3 2- Oxide – O 2-

9. Remember - Atoms like to have FULL electron shells!!

10. How is a sodium ion formed? 2.8.1 (partially full outer shell) 11 protons = +11 11 electrons = -11 Total charge = 0 Sodium atom: 11 protons = +11 10 electrons = -10 Total charge = +1 Sodium ion: loses 1 electron + [2.8] (full outer shell) Na Na

11. How is a magnesium ion formed? 2.8.2 (partially full outer shell) 12 protons = +12 12 electrons = -12 Total charge = 0 Magnesium atom: 12 protons = +12 10 electrons = -10 Total charge = +2 Magnesium ion: [2.8] 2+ (full outer shell) 2+ Mg Mg loses 2 electrons

12. How is a fluoride ion formed? 2.7 (partially full outer shell) 9 protons = +9 9 electrons = -9 Total charge = 0 Fluorine atom: 9 protons = +9 10 electrons = -10 Total charge = -1 Fluoride ion: [2.8] - (full outer shell) - F F gains 1 electron

13. [2.8.8] 2- (full outer shell) 2.8.6 (partially full outer shell) How is a sulfide ion formed? 16 protons = +16 16 electrons = -16 Total charge = 0 Sulfur atom: 16 protons = +16 18 electrons = -18 Total charge = -2 Sulfide ion: 2- S S gains 2 electrons

14. Calculating ion charges What is the charge on the ion of each element? +2 +2 +1 -3 -1 2.8.8.2 1 2.8.5 2.7 2.2 calcium hydrogen phosphorus fluorine beryllium Element Electron shells Charge on ion

15. What is a compound ion? 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 . hydroxide sulfate nitrate carbonate ammonium -1 -2 -1 -2 +1 Ion Formula Charge Atoms present NH 4 + CO 3 2- NO 3 - SO 4 2- OH - O O O O O O O O O O O H H H H H C N N S What atoms are present in the following compound ions?

16. What is Ionic Bonding? These compounds are usually formed by a reaction between a metal and a non-metal . The metal and non-metal atoms have incomplete outer electron shells and so are unstable . The positive and negative ions are strongly attracted to each other. This electrostatic attraction is called ionic bonding .

17. Dot and Cross Diagrams NaCl – Sodium Chloride - Cl Na +

18. What is the ratio of ions? Sodium chloride (NaCl) and magnesium oxide (MgO) are simple ionic compounds. Both compounds have a 1:1 ratio of metal ions to non-metal ions Na Cl Na + Cl - 1 electron Mg Mg 2+ O O 2- 2 electrons In each compound, the metal needs to lose the same number of electrons that the non-metal needs to gain.

19. What is the ratio of ions in 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 O O 2- Na + Na + 1 electron from each Na atom 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 Na 2 O.

20. What is the ratio of ions in 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. Mg Cl Mg 2+ Cl Cl - Cl - 1 electron for each Cl atom 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 MgCl 2 .

21. Questions What is the ratio of atoms in Aluminium Bromide? What is the ratio of atoms in Calcium Fluoride? What is the ratio of atoms in Aluminium Oxide?

22. Plenary Answer the following questions T or F: An ion is formed when an atom gains or losses electrons. An example of a cation is sulphate SO 4 2- . A positive metal ion is formed when electrons are lost from the metal atom. Ionic bonding is between a positive metal ion called a cation and a negative non-metal ion called an anion. It is the electrostatic attraction between these two ions. 5. Properties of ionic compounds are that they have low melting points, non-conductors of electricity when molten. T F T F T

23. More ionic formulae 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 O N Br S Cl LiF CaF 2 NaF MgF 2 AlF 3 KF Li 2 O CaO Na 2 O MgO Al 2 O 3 K 2 O Li 3 N Ca 3 N 2 Na 3 N Mg 3 N 2 AlN K 3 N LiBr CaBr 2 NaBr MgBr 2 AlBr 3 KBr Li 2 S CaS Na 2 S MgS Al 2 S 3 K 2 S LiCl CaCl 2 NaCl MgCl 2 AlCl 3 KCl

24. Connect Odd One Out – OOO Turn to the back of your books and note down which picture you think is the Odd One Out and WHY A B C

25. Learning Outcomes What We are investigating the properties of compounds formed from Ionic Bonding Why So we can describe the properties of Ionic compounds e.g. salt How By investigating the solubility and conductivity of ionic compounds.

26. Properties of Ionic Compounds Ionic substances form giant ionic lattices containing oppositely charged ions. They have high melting and boiling points,

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

28. Why do ionic compounds form crystals? Ionic compounds such as sodium chloride, form crystals, with a cubic shape. This is due to the structure of the ionic lattice. All ionic compounds form lattices and crystals when solid.

29. Heating ionic compounds Why are ionic compounds solid at room temperature and have high melting points and boiling points? 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. sodium chloride magnesium oxide Compound Ion charges Melting point ( o C) Boiling point ( o C) 1 + and 1 - 2 + and 2 - 801 1,413 2,852 3,600 strong ionic bonds hold ions together Ionic bonds are strong and a lot of heat is needed to break them.

30. How can ionic compounds conduct electricity? 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. As solids, ionic compounds cannot conduct electricity because their ions are bonded together in the lattice. ions in solid state cannot move 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.

31. Why are ionic compounds brittle? Ionic compounds are brittle – they shatter when they are hit. 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. repulsion force Ionic bonds are strong, so why does this happen?