Presentation on theme: "MYP Chemistry Ionic Bonding and Ionic Compounds"— Presentation transcript:
1MYP Chemistry Ionic Bonding and Ionic Compounds International College Spain
2Electron Configuration in Ionic Bonding OBJECTIVES:Use the periodic table to infer the number of valence electrons in an atom, and draw it’s electron dot structure.
3Electron Configuration in Ionic Bonding OBJECTIVES:Describe the formation of cations (positive ions) from metals, and of anions (negative ions) from non-metals.
4Valence ElectronsThe electrons responsible for the chemical properties of atoms are those in the outer energy level.Valence electrons - The electrons in the outer energy level or shellthe highest occupied energy levelInner electrons -those in the energy levels below.
5Keeping Track of Electrons Atoms in the same column...Have the same outer electron configuration.Have the same valence electrons.Easily found: same as the main group number on the periodic table.Group 2A: Be, Mg, Ca, etc.2 valence electrons
6X Electron Dot diagrams A way of keeping track of valence electrons. How to write them?Write the symbol.Put one dot for each valence electronDon’t pair up until they have to.X
7The Electron Dot diagram for Nitrogen Nitrogen has 5 valence electrons.First we write the symbol.NThen add 1 electron at a time to each side.Until they are forced to pair up.
9Electron Configurations for Cations Metals lose electrons to attain noble gas configuration.They make positive ions (cations)If we look at the electron configuration, it makes sense to lose electrons:Na 2,8,1 1 valence electronNa+ 2,8 noble gas configuration
10Electron Dots For Cations Metals will have few valence electrons (usually 3 or less)Ca
11Electron Dots For Cations Metals will have few valence electronsThese will come offCa
12Electron Dots For Cations Metals will have few valence electronsThese will come offForming positive ionsCa2+Pseudo-noble gas configurationNow make Sc an ion.
13Electron Configurations for Anions Nonmetals gain electrons to attain noble gas configuration.They make negative ions (anions)Halide ions- ions from chlorine or other halogens that gain electronsS 1s22s22p63s23p4 6 valence electronsS2- 1s22s22p63s23p6 noble gas configuration.
14Electron Dots For Anions Nonmetals will have many valence electrons (usually 5 or more)They will gain electrons to fill outer shell.PP3-
15Stable Electron Configurations All atoms react to achieve noble gas configuration.Noble gases have 8 outer shell (valence) electrons.Also called the octet rule.Ar
16Ionic Bonds The characteristics of an ionic bond. Ions held together by……..electrostatic attraction
17Ionic Bonds Characteristics of ionic compounds electrical conductors when melted and when in aqueous solution.High m.p.Brittle, hard crystals
18Properties of ionic compounds You are provided with three ionic compoundsFor each carry out the following testsHeat a sample strongly in a test tube.Add a spatula of the compound to 25 cm3 of water in a small beaker- stirTest the conductivity of the solutionRepeat using two spatulas
19Ionic BondingAnions and cations are held together by opposite charges.Ionic compounds are called salts.Simplest ratio is called the formula unit.The bond is formed through the transfer of electrons.Electrons are transferred to achieve noble gas configuration.
34Classwork problems (a) Show the bonding between the followingMagnesium and OxygenPotassium and ChlorineCalcium and FluorineLithium and NitrogenAluminium and Fluorine
35Homework problems These are slightly harder Magnesium and Phosphorus Beryllium and NitrogenCalcium and SulphurMagnesium and NitrogenAluminium and Oxygen
36Properties of Ionic Compounds Crystalline structure, usually solidsA regular repeating arrangement of ions in the solidIons are strongly bonded together.Structure is rigid.High melting pointsElectrical conductors when meltedElectrical conductors in solution
38Do they Conduct? Conducting electricity is allowing charges to move. In a solid, the ions are locked in place.Ionic solids are insulators.When melted, the ions can move around.Melted ionic compounds conduct.NaCl: must get to about 800 ºC.Dissolved in water they conduct (aqueous)
39Bonding in Metals OBJECTIVES: Use the theory of metallic bonds to explain the physical properties of metals.
40Bonding in Metals OBJECTIVES: Describe the arrangements of atoms in some common metallic crystal structures.
41Metallic Bonds How atoms are held together in the solid. Metals hold on to their valence electrons very weakly.Think of them as positive ions (cations) floating in a sea of electrons:
42Sea of Electrons + Electrons are free to move through the solid. Metals conduct electricity.+
43Metals are Malleable Hammered into shape (bend). Also ductile - drawn into wires.Both malleability and ductility explained in terms of the mobility of the valence electrons
47Ionic solids are brittle Strong Repulsion breaks crystal apart.+-+-+-+-
48Crystalline structure of metal If made of one kind of atom, metals are among the simplest crystalsBody-centered cubic:every atom has 8 neighborsNa, K, Fe, Cr, W
49Crystalline structure of metal 2. Face-centered cubic:every atom has 12 neighborsCu, Ag, Au, Al, Pb3. Hexagonal close-packedevery atom also has 12 neighborsdifferent pattern due to hexagonalMg, Zn, Cd
50Alloys We use lots of metals every day, but few are pure metals Alloys - mixtures of 2 or more elements, at least 1 is a metalmade by melting a mixture of the ingredients, then coolingBrass: an alloy of Cu and ZnBronze: Cu and Sn
51Why use alloys? Properties often superior to element Sterling silver (92.5% Ag, 7.5% Cu) is harder and more durable than pure Ag, but still soft enough to make jewelry and tablewareSteels are very important alloyscorrosion resistant, ductility, hardness, toughness, cost
52Why use alloys? Look up alloys in your text book Types? a) substitutional alloy- the atoms in the components are about the same sizeb) interstitial alloy- the atomic sizes quite different; smaller atoms fit into the spaces between largerAmalgam- dental use, contains Hg