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Published byRoger Garrett Modified over 8 years ago
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Unit 6 Ionic Compounds
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Remember… The electrons in the outermost level or shell are called… –Valence electrons You can determine the number of valence electrons in the s & p blocks by looking at the… –Group number
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Remember… Atoms in the same column have the same properties because they have the same… –Outer electron configuration –Number of valence electrons
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Stable Electron Configurations Atoms want to be stable! Stable = noble gas configuration –8 valence electrons (s 2 & p 6 ) Atoms are electrically neutral –Same # of protons and electrons –So neutral is not always stable….
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Atoms and ions So…some atoms will form ions to achieve that stable electron configuration Ions are atoms, or groups of atoms, with a charge –Different # of protons and electrons Only electrons can be added or removed since changing the number of protons changes the identity
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Remember… Elements differ by the number of protons Isotopes differ by the number of neutrons Ions differ by the number of electrons
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Forming Ions Some atoms LOSE electron(s) to achieve a noble gas configuration More protons than electrons so it becomes a positively charged ion + charged ion = Cation Occurs in metals
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Examples of Cations Na – 11 electrons - 1s 2 2s 2 2p 6 3s 1 –1 valence electron – VERY reactive Na + - 10 electrons - 1s 2 2s 2 2p 6 –Noble gas configuration - STABLE
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Electron Dots For Cations Metals have few valence electrons & lose them to become stable Ca
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Electron Dots For Cations Metals have few valence electrons & lose them to become stable Ca
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Electron Dots For Cations Metals have few valence electrons & lose them to become stable Forming a positive ion (cation) Ca 2+
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Forming Ions Some atoms GAIN electron(s) to achieve a noble gas configuration More electrons than protons so it becomes a negatively charged ion Negatively charged ion = Anion A Negative ION Occurs in nonmetals
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Examples of Anions S – 16 electrons - 1s 2 2s 2 2p 6 3s 2 3p 4 –6 valence electrons = REACTIVE S 2- - 18 electrons - 1s 2 2s 2 2p 6 3s 2 3p 6 –Noble gas configuration = STABLE
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Electron Dots For Anions Nonmetals have several valence electrons They will gain electrons to fill outer shell. P P 3-
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Practice Use electron dot diagrams to show how the following form ions Al Cl KK OO
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Periodic Trend for Ion Formation
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Atomic Number # of protons # of electrons Cl Cl - K K +
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Transition metals WEIRD! Form cations Hard to predict the charge Often will form more than 1 charge Can’t form noble gas configuration b/c it would take too much energy Still try to fill up orbitals or half orbitals
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Examples Zinc –1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 Zn 2+ –1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 –Full 3 rd energy level Fe 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2 Fe 2+ 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 4s 1 Fe 3+ 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5
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Naming ions Follows IUPAC rules Cations keep the name of the metal –Ca calcium –Ca 2+ calcium ion Anions change ending to –ide –Cl chlorine –Cl 1- chloride (ion)
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Naming Ions Transition metals use Roman numerals to indicate the charge (always positive) Fe 2+ = Iron (II) ion Fe 3+ = Iron (III) ion
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Polyatomic ions Groups of atoms that stick together as a unit, and have a charge Names often end in –ate or –ite You need to memorize the following 6: –PO 4 3- phosphate –CO 3 2- carbonate –SO 4 2- sulfate –NO 3 - nitrate –OH - - hydroxide –NH 4 + - ammonium
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Polyatomic Ions
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Stable Electron Configurations Atoms want to be stable! Stable = noble gas configuration –8 valence electrons (s 2 & p 6 ) Also called the octet rule –In forming compounds, atoms try to obtain 8 electrons in the highest energy level
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Achieving Stability Forming ions Bonding with other ions to form an ionic compound
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Ionic Bonding Anions and cations join together to form ionic compounds (AKA salts) The bond is formed through the transfer of electrons to achieve noble gas configuration
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Ionic Bonding NaCl 1+ 1-
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Ionic Compounds (Salts) Made up of –a positive and negative ion –a cation and an anion –a metal and a nonmetal (or polyatomic ion) Simplest ratio of elements = formula unit
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Properties of Ionic Compounds Crystalline structure –A regular repeating arrangement of ions –Dissolves into electrolytes –Structure is rigid –Ions are strongly bonded (Legos)
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Crystalline structure
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Properties of Ionic Compounds High melting points- because of strong forces between ions Good conductors of electricity when dissolved in water or melted
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Ionic Bonding - DOTS All the electrons must be accounted for! CaP
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Ionic Bonding CaP
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Ionic Bonding Ca 2+ P
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Ionic Bonding Ca +2 P Ca
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Ionic Bonding Ca 2+ P 3- Ca
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Ionic Bonding Ca 2+ P 3- Ca P
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Ionic Bonding Ca 2+ P 3- Ca 2+ P
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Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca
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Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca
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Ionic Bonding Ca 2+ P 3- Ca 2+ P 3- Ca 2+
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Ionic Bonding Ca 3 P 2 “Formula Unit”
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Practice Use electron dot diagrams to show how the following elements make an ionic compound and write the formula unit Mg and Cl
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Practice Na and N
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Practice Al and O
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Writing formulas Ionic compounds have no overall charge So we add the correct subscripts to represent the # of atoms that balance the ions
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Writing Formulas – Criss-Cross 1. Write the ions side by side. Fe 3+ S 2-
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Writing Formulas – Criss-Cross 2. Draw arrows that cross each other. Fe 3+ S 2-
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Writing Formulas – Criss-Cross 3. Put the charge at the ends of the arrows. Fe 3+ S 2- 23
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Writing Formulas – Criss-Cross 4. Write the formula by using the numbers at the ends of the arrows as subscripts Fe 3+ S 2- 23 Fe 2 S 3
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Writing Formulas – Criss-Cross Make sure you reduce when needed! –Iron (II) Oxide
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Using Polyatomic Ions Same rules but put a bracket around the entire ion before adding the subscript Na + OH - = NaOH Mg 2+ OH - = Mg[OH] 2 Na + CO 3 2- = Na 2 CO 3 Cu 2+ PO 4 3- = Cu 3 [PO 4 ] 2
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Naming AKA Nomenclature First name the cation, then the anion Cation –Usually the same name as the metal –If a transition metal (or Sn or Pb), name the metal and use a roman numeral for the charge of the ion.
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Naming Ionic Compounds Anion –Ends with –ide If a polyatomic ion is in the compound, don’t change the name, just name it.
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Examples NaCl –Cation = Na (sodium) –Anion = Cl (chlorine) ide Sodium Chloride
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MgBr 2 –Cation = Mg (magnesium) –Anion = Br (bromine) ide Magnesium bromide
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NaOH –Cation = Na (sodium) –Anion = OH (hydroxide) Sodium hydroxide MgSO 4 Cation = Mg (magnesium) Anion = SO 4 (sulfate) Magnesium sulfate
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FeCl 2 –Cation = Fe (Iron) –Anion = Cl (chlorine) ide Which iron is this? Use split method OR Algebra method Iron (II) chloride
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Name Formula 1.Start by writing the symbols of each element. 2.Then add the charges of each ion. 3.Use subscripts to balance the charges. (criss cross, etc.)
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Name Formula Sodium sulfide Iron (III) chloride
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Ionic Bonding Ionic bonds form between… –Metals & Nonmetals But it is possible for nonmetals to bond to each other –Covalent bond And for metals to mix with each other –Alloy
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Alloys SSolutions made by dissolving metal into other elements (usually metals) MMade by melting them together and cooling them IIf the atoms of the metals are about the same size, they substitute for each other CCalled a substitutional alloy
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Metal A Metal B + Substitutional alloy Bronze – Copper and Tin Brass- 60 % Copper 39% Zinc and 1%Tin 18 carat gold- 75% gold, 25%Ag or Cu
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Alloys If the atoms of the metals are different sizes, the small one will fit into the spaces of the larger one Called an interstitial alloy
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Metal A + Metal B Interstitial Alloy Steel – 99% iron 1 % C Cast iron- 96% Iron, 4%C
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Alloys Making an alloy is still just a mixture Blend the properties Designed for a purpose
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For Your Quiz Valence electrons Elements vs Isotopes vs Ions Cation vs Anion Naming Ions KNOW YOUR POLYATOMIC IONS Characteristic Properties of Salts Ionic bond forms between…. Naming compounds/ writing formulas Alloys
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