2 Welcome Back! October 19th, 2011 Brainteaser:Let’s reflect on last quarter’s performance:What are some things you thought you did well for this class?What are some things you think you could improve for this quarter?What is your overall goal for this quarter (i.e. what do you want to accomplish this quarter and how are you going to do it?)
3 Agenda Brainteaser Unit 5: Ionic Bonding Notes Homework Ionic Bonding Practice Worksheet
4 Unit 4: Chemical Bonding Differences in chemical behavior are due to differences in the types of bondsBond: forces that hold atoms together in molecules or ionic compounds.
5 Chemical Bonding Types of bonds and types of substances Ionic Covalent MetallicThe type of bond between atoms is partially responsible for the properties of the substance.
6 Chemical Bonding Bonding Involves the valence electrons or outermost shell (or highest shell) electronsFor group A elements – the group number tells how many valence electronsFor example:K, Ca, C, B, N, F, NeLewis Dot Structures show the valence electrons around an atom and for most molecules and compounds a complete octet for the elements is needed.For example: N, Al, H2O
7 Lewis Dot Structures These symbols are called Lewis symbols We generally place the electrons on four sides of a square around the element symbol.
8 Drawing Lewis Dot Structure Place DOTS around the SYMBOL clockwise pairing up dots on the second time aroundFor example:Magnesium (Mg) and Oxygen (O) MgOMgO
14 Transition ElementsNot periodic; +2 and +3 common
15 Charges and Formulas of Oxoanions Oxoanions generally have the same charge as the simple anion of the same nonmetal.Related to position in the periodic table; note exceptions for B, C, NPolyatomic Ionstend to reflectthe charge of the base element
16 Ionic Bonds form when… A cation (metal) bonds with an anion (nonmetal) A salt is formed:For example: Sodium: Na “metal” bonded to Chlorine: Cl “nonmetal”For example: Magnesium: Mg “metal” bonded to Chlorine: Cl “nonmetal”
17 Ionic Bonding: The Formation of Sodium Chloride Sodium has 1 valence electronChlorine has 7 valence electronsAn electron transferred giveseach an octetNa: 1s22s22p63s1Cl: 1s22s22p63s23p5
18 Ionic Bonding: The Formation of Sodium Chloride This transfer forms ions, each with an octet:Na+ 1s22s22p6Cl- 1s22s22p63s23p6
19 The resulting ions come together due to electrostatic attraction (opposites attract):The resulting ions come together due to electrostatic attraction(opposites attract):The resulting ions come together due to electrostatic attraction(opposites attract):The resulting ions come together due to electrostatic attraction(opposites attract):Na+Cl-Na+Na+Cl-The net charge on the compound must equal zeroThe net charge on the compound must equal zero
20 Lewis Dot DrawingIonic bondExampleLewis Dot diagramA positively charged ion is attracted to a negatively charged ion.A transfer of electronsMetal and a Non-MetalNaClA positively charged ion is attracted to a negatively charged ion.A transfer of electronsMetal and a Non-MetalNaClA positively charged ion is attracted to a negatively charged ion.A transfer of electronsMetal and a Non-MetalNaClNaCl
21 Practice Draw the Lewis dot structures for the following compounds: CaOBaCl2Na2S
22 Writing Formulas for Ionic Compounds Crisscross MethodExample:Ca and FWrite the element symbols for the cation and anion, with the cation on the left and the anion on the right.Write each ion’s charge as a superscript.Crisscross the two charges moving them downward diagonally from one superscript to the other subscript.
23 PracticeWrite the correct formula for the ionic compounds composed of the following pairs of ions using the crisscross method:Potassium and iodideMagnesium and chlorideAluminum and bromideCesium and nitrideBarium and sulfideIron (II) and fluoride
25 Warm Up Write the correct formula for these ionic compounds: Aluminum oxideBarium nitrideIron (III) oxideMagnesium carbide
26 Agenda Brainteaser Grade Homework: Practice W/S Unit 5 Notes: Naming Ionic CompoundsProperties of Ionic CompoundsPartner Bonding ActivityHomework:Naming Ionic bonds W/S
27 Naming Ionic Compounds Step 1:Cation is written first in the name; anion is written second in the nameName of cation is the same as the neutral atom element (Na+ = Sodium)Step 2:Anion is written by adding the suffix –ide to the root of the element name (I- = iodide)For example: NaCl = Sodium Chloride, Al2O3 = Aluminum oxideStep 3:Figure out if you need a Roman numeral in the name (transition metals).Figure out what the Roman numeral should beFor example: Fe2O3Step Four: Check your work
28 Practice Naming Ionic Compounds KFAlF3KClNa3PFe2O3
29 Properties of Ionic Bonding Definition:In an ionic bond, a positively charged ion is attracted to a negatively charged ionElectrostatic Attraction
30 Properties of Ionic Bonding Solid at room temperatureElectrical conductivityConducts electricity when dissolved in water or in liquid (molten) formDissociated ions can carry charge through the solutionHardnessHard but brittleElectrostatic repulsionMelting points and Boiling pointsHigh melting and boiling pointForces of attraction between positive and negative ions are strong