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Ionic Compounds

Ionic Compounds. Elements vs. Compounds. Elements are composed of one type of atom Elements are represented by a symbol which consists of only 1 capital letter. C Au Chlorine Sodium. carbon. gold. Cl. Na. Compounds are composed of two or more elements.

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Ionic Compounds

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  1. Ionic Compounds

  2. Elements vs. Compounds • Elements are composed of one type of atom • Elements are represented by a symbol which consists of only 1 capital letter C Au Chlorine Sodium carbon gold Cl Na

  3. Compounds are composed of two or more elements. • Compounds are represented by a formula which consists of 2 or more element symbols written next to each other. • Usually the least electronegative element is first. NaCl NH4C2H3O2 1 sodium, 1 chloride 1 Nitrogen, 7 Hydrogen, 2 Carbon, 2 Oxygen

  4. Objective 5 and 6 Reading the Composition of a Formula CO CO2 CoBr2 (NH4)3PO4 1 carbon, 1 oxygen 1 carbon, 2 oxygen 1 cobalt, 2 bromine 3 nitrogen, 12 hydrogen, 1 phosphorus, 4 oxygen

  5. Objectives 1 and 3 Ionic Compounds Contain a positive ion (cation) and a negative ion (anion). Usually a metal and a nonmetal, or may contain a polyatomic ion.

  6. Objective 1 Molecular compounds Compounds composed of ONLY nonmetals. Do not contain ions. Will be dealt with in the next unit. N2O4 H2O2 C6H12O6

  7. Objective 2 Formula Units The lowest ratio of elements in a compound. Also known as the empirical formula. Written for ionic compounds. (they form crystals)

  8. Empirical vs Molecular formulas • Empirical formulas show the elements in the lowest ratio possible. NO2 HO CH2O AlBr3 • Molecular formula state the actual number of each atom present. N2O4 H2O2 C6H12O6 AlBr3

  9. Ionic compounds • Ionic compounds are always written as empirical formulas. They represent a formula unit for the ionic crystal. CaCl2 Fe2O3 AgNO3

  10. Law of Definite Proportions • In a particular compound the masses of an element are always in the same proportions. CO2 is carbon dioxide CO is a different ratio and so a different compound called carbon monoxide

  11. Formation of ions • Octet Rule – in forming compounds atoms will try to obtain a noble gas electron configuration. • To do this metals ________ electrons and nonmetals _________ electrons lose gain

  12. Metal Examples . Na atom = 1s22s22p63s1 Na Na1+ = 1s22s22p6 Na1+ Note the 3rd energy level electron was lost to have the same electron configuration as neon Ne = 1s22s22p6

  13. You try x :Ca Ca = Ca2+ = What noble gas does Ca2+ resemble? 1s22s22p63s23p64s2 Ca2+ 1s22s22p63s23p6 The oxidation number on the metal ion (cation) is the positive value of how many electrons were lost.

  14. Naming metal ions • Metal ions names stay the same as their element name EXCEPT if the metal has more than one oxidation number. (Look on your Elements and Ions to Know handout to find multiple oxidation numbers)

  15. Naming metal ions If there is more than one oxidation number write the name of the element followed by its oxidation number written in Roman numerals and placed in parenthesis. Ex. Fe+2 Iron (II)/Ferrous Fe+3 Iron (III)/Ferric Cu+1 Copper (I)/Cuprous Cu+2 Copper (II)/Cupric

  16. Examples Magnesium ion • Mg2+ • Fe3+ • Al3+ • Fe2+ • Tin (IV) • Copper (I) • Silver Iron (III) ion Aluminum ion Iron (II) ion Sn4+ Cu1+ Ag1+

  17. Nonmetals . • Cl atom = 1s22s22p63s23p5 :Cl: • Cl1- = 1s22s22p63s23p6 :Cl:1- .. .. .. Note the 3rd energy level electron was lost to have the same electron configuration as argon Ar = 1s22s22p63s23p6

  18. .. .. You try . O = O2- = What noble gas does O2- resemble? 1s22s22p4 :O. .. 1s22s22p6 :O:2- The oxidation number on the nonmetal ion (anion) is the negative value of how many electrons were gained to obtain a noble gas structure.

  19. Naming nonmetal ions • If the ion is composed of one element: name the element but change its ending to “ide”. • If the ion is composed of two or more elements: name the polyatomic ion (either memorized or looked up on a polyatomic ion chart.)

  20. Naming nonmetal monoatomic ionsend in “-ide” • Cl1- • S2- • F1- • O2- Chloride ion Sulfide ion Fluoride ion Oxide ion Notice how close the spellings are, SPELLING COUNTS!!!!

  21. Naming nonmetal polyatomic ionsmost end in “-ate”, “-ite” SO42- • Sulfate ion • Hydroxide ion • Sulfite ion • Nitrate ion • Acetate ion OH1- SO32- NO31- C2H3O21- Notice how close the spellings are, SPELLING COUNTS!!!!

  22. Ionic Bonds – The achievement of the "noble gas configuration" by electron transfer from metallic atoms to non-metallic atoms. The electrostatic bond is formed between positively charged metallic ions (cations) and negatively charged non-metallic ions (anions). LINK NaCl table salt LINK

  23. Crystal Formation

  24. Ionic Bonds: MgO (magnesium oxide) - 2 e- Mg2+ ion, r = 0.6Å Mg atom, r = 1.6Å + 2 e- O atom, r = 0.78Å O2- ion, r = 1.32Å LINK

  25. Writing Formulas • The total of the charges must be zero. • Subscripts multiplied by the cation charge are added to the subscript multipled by the anion charge to total zero. • Ca2+ Br1-  CaBr2 1(2+) + 2(1-) = 0 where the underlined numbers become the subscripts.

  26. Writing Formulas Cont. • (NH4)1+ S2-  (NH4)2S 2(1+) + 1(2-) = 0 where the underlined numbers become the subscripts. • Ba2+ (PO4)3-  Ba3(PO4)2 3(2+) + 2(3-) = 0 where the underlined numbers become the subscripts.

  27. Naming Ionic Compounds • Name the metal ion – remember to use roman numerals if there is more than one possible oxidation number • Name the nonmetal or polyatomic ion • Example: ZnCl2 KOH | Zinc chloride | Potassium hydroxide

  28. More than one oxidation state • The oxidation number must be found for the metal. • Remember all compounds are electrically neutral. (cation charge + anion charge = 0) CuCl2 1(Cux) + 2 (Cl1-) 1x + 2(-1) =0 x= 2 Copper (II) chloride

  29. NiS 1(Nix) + 1(S2-) 1(X) + 1(-2) =0 x = 2 Nickel (II) Sulfide Sn(SO4)2 1(Snx) + 2(SO42-) 1(x) + 2(-2) = 0 x = 4 Tin (IV) sulfate

  30. Special Ionics: Acids

  31. Generally Acids have formulas that begin with H (hydrogen) HCl(aq) H3PO4(aq) H2CO3(aq) H2SO4(aq) HF(aq) HBr(aq) Notice they all have (aq) written beside the formulas, this indicates they are dissolved in water or aqueous.

  32. Naming 2 Element Acids Remember this is for acids with: hydrogen and one other element Such as HCl 1. Start the name with hydro • Finish with the nonmetal changing its ending to “ic” Ex. HCl = hydro chloric acid

  33. Naming Acids with Polyatomic Ions Name the polyatomic ion in the acid (look up on a polyatomic ion sheet if you need to) If the polyatomic ion ends in “ate” change the ending to “ic” Ex. H2CO3 polyatomic ion = carbonate change to = add = Final name: carbonic acid Carbonic acid

  34. If the polyatomic ion ends in “ite” change the ending to “ous” Example: HNO2 polyatomic ion = nitrite change to = add = Final name: nitrous acid nitrous acid

  35. Careful of odd ones: • Sulfate turns to sulfuric • Sulfite turns to sulfurous • Phosphate turns to phosphoric • Phosphite turns to phosphorous

  36. Writing Acid Formulas • ALWAYS start with H • Decide what the anion is. remember: if it starts with hydro, look for a nonmetal element and find its oxidation number. Example: hydrobromic acid H+1 Br1- Bromic sounds like bromine Bromine has a -1 charge so.., HBr(aq)

  37. If it has no prefix but ends in “ic” look for a polyatomic ion that has the same root word but ends in “ate”. Find the polyatomic ions formula and charge Example: chromic acid Polyatomic ion: chromate - CrO42- Ions involved: H1+ CrO42- Formula: H2CrO4(aq)

  38. If it has no prefix but ends in “ous” look for a polyatomic ion that has the same root word but ends in “ite”. Find the polyatomic ions formula and charge Example: sulfurous acid Polyatomic ion: sulfite - SO32- Ions involved: H1+ SO32- Formula: H2SO3(aq)

  39. Acid Review • Acids have two names Hydrogen Bromide or Hydrobromic Acid. Hydrogen nitrate or Nitric Acid. • Binary acids are formed from hydrogen and one other element. They are named Hydro-element-ic Acid. • Polyatomic Ions attached to hydrogens change their endings. --ate becomes –ic and –ite becomes –ous. HNO3 is hydrogen nitrate so it becomes Nitric acid.

  40. Properties of Ionic Compounds • The strong attractions between the cations and the anions in ionic solids are responsible for their high melting points. For ionic compounds, melting points typically range from 300oC to 1000oC. • Ionic compounds are soluble in water. • In aqueous solution, an ionic compound dissociates into its ions. • This means that when NaCl is dissolved in water, the solution contains Na+ ions and Cl- ions. • The dissociated ions in aqueous solution gives the solution the ability to conduct electricity. Therefore, ionic compounds dissolved in water makes strong electrolytes.

  41. Metallic Solid • Infinite array of atoms held together by metallic bonding • Metallic bonding is like positive metal ions in a sea of freely-moving negative electrons • Metallic bonding is moderate to strong • Properties: • moderate-to-high melting point, boiling point • may be hard or soft • electrically conductivesolid and liquid • malleable, ductile • lustrous

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