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Ionic Compounds

Ionic Compounds . Ions and Ion formation. Ions are atoms with a charge due to more or fewer electrons then protons . Ions and the octet rule . Br. P. Ne. Al. Ca. Ar (3). Ne (0). Ne (3). Ar (2). Noble gas. Kr. (spaces). (1). –. Br. Ion. P 3–. none. Al 3+. Ca 2+.

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Ionic Compounds

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  1. Ionic Compounds

  2. Ions and Ion formation • Ions are atoms with a charge due to more or fewer electrons then protons

  3. Ions and the octet rule Br P Ne Al Ca Ar (3) Ne (0) Ne (3) Ar (2) Noble gas Kr (spaces) (1) – Br Ion P 3– none Al 3+ Ca 2+ • Ions of s and p block elements form in order to have a lower energy state by being isoelectronic to a noble gas.

  4. Overview: Types of Bonds • 3 bond types : ionic, covalent, and metallic • In ionic bonding one atom has a stronger attraction for electrons than the other, and “steals” an electron from a second atom. Oppositely charged ions stick together. • In covalent bonding the attraction for electrons is similar for two atoms. They share their electrons to obtain an octet • In metallic bonds, electrons are in a delocalized electrons, not tied to a particular nucleus. covalent ionic metallic

  5. Predicting Bond Type and Bond Properties Metal – Nonmetal: • Ionic Bond • Forms a Salt = network solid or crystal • A very strong bond • Expressed as a formula unit

  6. Predicting Bond Type and Bond Properties Nonmetal – Nonmetal: • Covalent bond • Forms a Molecule • A weaker bond • Expressed as a chemical formula Methane, CH4 Water

  7. Predicting Bond Type and Bond Properties Metal - Metal: • Metallic bond • Forms an Alloy • A mixture of metals with delocalized electrons

  8. Bond Identification PracticeA) ionic, B) covalent, or C) metallic? 1) MgO 2) CaCl2 3) SO2 4) PbCl2 5) CCl4 6) CH4 7) AuCu

  9. Bond Identification PracticeA) ionic, B) covalent, or C) metallic? 2)CaCl2 (ionic), 3) SO2 (covalent), 1) MgO (ionic), 4) PbCl2 (covalent), (ionic), 5) CCl4 6) CH4 (covalent), (metallic) 7) AuCu

  10. e– 1) 2) Na Na+ Cl Cl– Cl– Na+ Ionic bonding • Ionic bonding involves 3 steps (3 energies) • 1) loss of an electron(s) by one element, 2) gain of electron(s) by a second element, 3) attraction between positive and negative 3) Cation = positive ion Anion = negative ion

  11. 1e- 3p+ 3p+ 17p+ 2e- 2e-1e- 7e- 8e- 2e- 17p+ 8e-8e-2e 4n0 18n0 4n0 18n0 Cl [Li]+ [Cl]– Li Ionic bonding (Li + Cl) • Ionic bonding (stealing/transfer of electrons) can be represented in three different ways Li + Cl [Li]+[Cl]–

  12. 8p+ 8p+ 8e- 2e- 6e- 2e- 8n0 8n0 1e- 12p+ 12p+ 2e- 8e- 2e- 8e- 2e- 12n0 12n0 1e- O [Mg]2+ [ O ]2– Mg Ionic bonding: Mg + O Mg + O  [Mg]2+[O]2– For more lessons, visit www.chalkbored.com

  13. Structure of Ionic Compounds • They form network solids, also known as crystals. • Positive and negative ions surround each other. Si4+ and O2-

  14. Enthalpy • heat of reaction and change in enthalpy are used interchangeably for a reaction at constant Pressure ∆H = Hproducts - Hreactants endothermic: + ∆H exothermic: - ∆H Reactants Products 2H2 + O22 H2O

  15. Effects of a Catalyst on Activation Energy The catalyst speeds up the reaction by lowering the activation energy. A Which graph is Exothermic? Which is Endothermic? In which graph is ΔH negative? In which graph is ΔH positive? B

  16. Energy Transfer • Removing electrons uses energy (endothermic) ΔH = 495 kJ/mol Na + 495 kJ/mol  Na+ + e- • Adding electrons releases energy (exothermic)ΔH = -349 kJ/mol Cl + e-  Cl- + 349 kJ/mol • Salt formation releases energy (exothermic) ΔH = -411 kJ/mol Na+ + Cl-  NaCl + 411 kJ/mol • The net energy transfer determines if the overall reaction enthalpy (ΔH) is exo- or endothermic. ΔHrxn= 495 kJ/mol + (-349 kJ/mol) + (-411 kJ/mol) = -265 kJ/mol (Watch making sodium chloride video)

  17. Properties of Salts • High melting points and boiling points. • Solid salts do not conduct electricity. • Salt solutions are good conductors of electricity. CTD – Conductivity, temperature, depth

  18. Ionic Nomenclature: Monoatomic Ions • It’s easy, just name the positive ion first and then the negative ion, but change the negative ions last three letters to –ide. • If more than one ion exists for a metal, use a roman numeral to show which one. • Examples: 1) NaCl = 2) CaF2 = 3) Fe2O3 = 4) PbO = Hint: Look at the opposite (negative) ion to determine Roman numeral of transition metals. sodium chloride calcium fluoride iron (III) oxide lead (II) oxide

  19. Predicting Salt Formulas – The Crossing Rule Steps: • Look up ion charges (periodic table) • Switch the numbers and drop the charges • Reduce if possible Salts are neutral so think: Balance the charges!!

  20. You Try ZnBr2 • What is the formula of zinc bromide? • What is the formula of copper (II) oxide? • What is the formula of copper (I) oxide? • What is the formula of Tin (IV) sulfide? CuO Cu2O SnS2

  21. Ionic Nomenclature: Polyatomic Ions • Some groups of covalently bonded atoms act as ions, many of which are negative (see the back of your periodic table for a list of ions and the names). • Name them just like the monoatomic ions using the names from the back of the periodic table. Example: SeO42- = selenate, so: K2SeO4 = potassium selenate

  22. You Try • NaNO3 = • Ca3(PO4)2 = • Pb3(C6H5O7)4 = sodium nitrate calcium phosphate lead (IV) citrate

  23. The crossing rule and Polyatomic Ions • Hint: use parenthesis to separate numbers.

  24. You Try • Lithium thiosulfate • Ammonium phosphate • Bismuth (III) dichromate Li2S2O3 (NH4)3PO4 Bi2(Cr2O7)3

  25. Silicates • Rocks containing crystalline materials are called minerals. • Silicates are a class of mineral whose anions contain silicon and oxygen, such as Si4O12-10 found in Mg3(Si4O12)2 • Silicates make up much of the Earth’s crust.

  26. Learn the following prefixes (very important): • Prefix Number Value • Hemi- ½ • Mono- 1 • Di- 2 • Tri- 3 • Tetra- 4 • Penta- 5 • Hexa- 6 • Hepta- 7 • Octa- 8 • Nona- 9 • Deca- 10 • Doci- 12 Hydrates • Hydrates are salts with water bonded into their formula. • Hygroscopic means to absorb water. • Anhydrous means the salt without the water.

  27. Hydrate Nomenclature and Formulas • The name of the salt is followed by a prefix for how much water and the word “hydrate.” Ex. BaCl3.2H20 = • Use the crossing rule the same as before and then “add” the water indicated to write the formula from the name. Ex. Iron (III) nitrate nonahydrate = barium chloride dihydrate Fe(NO3)3.9H20

  28. You Try Name: • (NH4)2C2O4.H20 • CoCl2.6H20 Give the correct formula 3. Sodium acetate trihydrate 4. Barium hydroxide octahydrate Ammonium oxalate monohydrate Cobalt (II) chloride hexahydrate NaC2H3O2.3H20 Ba(OH)2.8H20

  29. The End • Next: Oxidation States, Covalent Bonding, Molecular Geometry, and more…

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