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HRW Ch 7 Chemical Formulas and Compounds pp

HRW Ch 7 Chemical Formulas and Compounds pp. Naming Compounds Writing Formulas. 7.1 Chemical Names & Formulas. Explain the significance of a chemical formula. Find the formula of a binary ionic compound. Name an ionic compound, given its formula.

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HRW Ch 7 Chemical Formulas and Compounds pp

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  1. HRW Ch 7 Chemical Formulas and Compounds pp Naming Compounds Writing Formulas

  2. 7.1 Chemical Names & Formulas • Explain the significance of a chemical formula. • Find the formula of a binary ionic compound. • Name an ionic compound, given its formula. • Use prefixes to name a binary molecular compound from its formula. • Write the formula of a binary molecular compound, given its name.

  3. Systematic Naming • Used because are too many compounds to remember the common names of all. • A Compound is made of two or more elements. • Put together from atoms. • The name should tell us how many andwhat type of atoms. • A quick review . . .

  4. Periodic Table • More than a list of elements. • Elements are put into columns because of similar properties. • Each column is called a group.

  5. Representative elements 1A 0 5A 7A 2A 3A 4A • The group A elements 6A

  6. Metals

  7. Metals • Luster – shiny. • Ductile – drawn into wires. • Malleable – hammered into sheets. • Conductors of heat and electricity.

  8. Transition metals • The Group B elements

  9. Non-metals • Dull • Brittle • Nonconductors - insulators

  10. Metalloids or Semimetals • Properties of both • Semiconductors

  11. Atoms vs. ions • Atoms are electrically neutral. • Same number of protons and electrons. • Ions are atoms, or groups of atoms, with a charge. • Different numbers of protons and electrons. • Only electrons can move. • Gain or lose electrons.

  12. Anion • Anegative ion. • Has gained electrons. • Nonmetals can gain electrons. • Charge is written as a superscript on the right. F-1 Has gained one electron O-2 Has gained two electrons

  13. Cation • Positive ions. • Formed by losing electrons. • More protons than electrons. • Metals form cations. K+1 Has lost one electron Ca+2 Has lost two electrons

  14. Compounds • Follow the Law of Definite Proportion. • I.e., have a constant composition. • Have to add the same number of atoms every time. • Two types . . .

  15. Two Types of Compounds • Molecular compounds • Made of molecules. • Made by joining nonmetal atoms together into molecules. • Share electrons.

  16. Two Types of Compounds • Ionic Compounds • Made of cations and anions. • Metal plus nonmetal. • The electrons lost by the cation are gained by the anion. • The cation and anions surround each other. • Smallest piece is a FORMULA UNIT.

  17. Two Types of Compounds Ionic Molecular Smallest piece Formula Unit Molecule Types of elements Metal and Nonmetal Nonmetals Solid, liquid or gas State solid Melting Point High >300ºC Low <300ºC

  18. Chemical Formulas • Shows the kind and number of atoms in the smallest piece of a substance. • Molecular formula - number and kinds of atoms in a molecule. • CO2 • C6H12O6 • Hydrocarbon - has only H and C • E.g., C8H18

  19. Formula Unit • The smallest whole number ratio of atoms in an ionic compound. • Ions surround each other so you can’t say which is hooked to which. • LD 2: 7.4, 7.5 CaF2 rotation & lattice

  20. Crystalline structure

  21. Charges on ions • For most of the Representative elements, the Periodic Table can tell us what kind of ion they will form from their location. • Elements in the same group have similar properties. • This includes having the same charge when they are ions.

  22. “1 plus . . .” chant +1 +2 +3 -3 -2 -1

  23. What about the transition metals? • We have to figure those out some other way. • More on this later.

  24. Naming Monoatomic Cations pp • We will use the systematic way. • If the charge is always the same (i.e., Group A metal) just write the name of the metal and add “ion”. • Transition metals have more than one type of charge (except Ag, Zn, Cd). • Indicate their charge (vs. the subscript) with roman numerals in parentheses.

  25. Exceptions to Roman Numerals pp • Transition metals need Roman numerals except for the following: • 1. Zinc, Zn, always forms a +2 ion, so it doesn’t need roman numerals. • ZnCl2 is zinc chloride (not zinc(II) chloride). • 2. Silver, Ag, always forms a +1 ion • AgCl is silver chloride. • 3. Cadmium, Cd, always forms a +2 ion. • 4. Scandium, Sc, always forms a +3 ion

  26. Tr39A Table 7.1 p 205 Common Monoatomic Ions What’s suffix for (-) ion? -ide How many e-s has Sr ion lost? 2 How name (+) ions? Adding “ion” to atom’s name. What’s the formula for potassium sulfide? K2S

  27. Na+1 Ca+2 Al+3 Fe+3 Fe+2 Pb+2 Li+1 Sodium ion Calcium ion Aluminum ion Iron(III) ion Iron(II) ion Lead(II) ion Lithium ion Name these

  28. Potassium ion Magnesium ion Copper(II) ion Chromium(VI) ion Barium ion Mercury(II) ion Mercury(I) ion K1+ Mg2+ Cu2+ Cr6+ Ba2+ Hg2+ Hg22+ (not Hg1+) Write Formulas for these

  29. Naming Monoatomic Anions • Monoatomic anions are always named by the same method. • Change the element ending to – ide • F-1 Start with the element “Fluorine”

  30. Naming Anions • Anions are always the same. • Change the element ending to – ide • F-1 Fluorin

  31. Naming Anions • Anions are always the same • Change the element ending to – ide • F-1 Fluori

  32. Naming Anions • Anions are always the same • Change the element ending to – ide • F-1 Fluor

  33. Naming Anions • Anions are always the same • Change the element ending to – ide • F-1 Fluori

  34. Naming Anions • Anions are always the same • Change the element ending to – ide • F-1 Fluorid

  35. Naming Anions • Anions are always the same • Change the element ending to – ide • F-1 Fluoride

  36. Cl-1 N-3 Br-1 O-2 Ga+3 Chloride Nitride Bromide Oxide Galliumion Name these

  37. Sulfide ion Iodide ion Phosphide ion Strontium ion S2- I1- P3- Sr2+ Write these

  38. Writing Formulas • The charges have to add up to zero. • Get charges on the pieces. • Cations from name of table. • Anions from table or polyatomic. • Balance the charges by adding in the subscripts. • Put polyatomics in parentheses.

  39. Writing Binary Ionic Compounds • Binary Compounds - composed of only two different elements. • E.g., Lead (IV) oxide • 1.Write symbols side by side, cation 1st. • Pb4+ O2- • 2. “Cross” the charges using the absolute value of the other ion. • Pb24+ O42-

  40. Writing Binary Ionic Compounds • E.g., Lead (IV) oxide • 1. Pb4+ O2- (“cross the charges” to balance) • 2. Pb24+ O42- • 3. Divide subscripts by largest common factor and also “erase” the charges. • PbO2 • (Do not divide the subscripts with molecules, only with ionic compounds).

  41. Easier way to “equalize” the charges • Formula: MgBr2 • One ion’s charge number is the number of atoms for the opposite element • “Criss-cross applesauce” Mg2+ Br1-

  42. Al3+ O2- Al2O3 2(+3) = +6 3(-2) = -6 (+6) + (-6) = 0

  43. Ca2+ O2- Ca2O2 can be reduced (formula unit) CaO

  44. Writing Formulas • Write the formula for calcium chloride . . . • Calcium is Ca+2 • Chloride is Cl-1 • Ca+2 Cl-1 would have a net +1 charge. • Need another Cl-1 • Ca+2 Cl2-1

  45. Learning Check Write the correct formula for the compounds containing the following ions: A. Na+, S2- 1) NaS 2) Na2S 3) NaS2 2) Na2S B. Al3+, Cl- 1) AlCl3 2) AlCl 3) Al3Cl 1) AlCl3 C. Mg2+, N3- 1) MgN 2) Mg2N3 3) Mg3N2 3) Mg3N2

  46. Lithium sulfide tin (II) oxide tin (IV) oxide Magnesium fluoride Copper (II) sulfide Iron (III) phosphide gallium nitride Iron (III) sulfide Li2S SnO SnO2 MgF2 CuS FeP GaN Fe2S3 Write the formulas for these

  47. Ammonium chloride ammonium sulfide barium nitrate NH4Cl (NH4)2S Ba(NO3)2 Write the formulas for these

  48. Things to look for pp • If cations have ( ), the roman numeral is their charge. • Iron (III) is Fe3+ • If anions end in -ide they are probably off the periodic table (Monoatomic) • If anion ends in -ate or -ite it is polyatomic and contains oxygen.

  49. Naming Binary Ionic Compounds pp • Binary Compounds - 2 elements. • Ionic - a cation and an anion. • To write the names just name the two ions. • Easy with Representative elements. • Group A (groups 1-2, 13-18) • NaCl = Na1+ Cl1- = sodium chloride • MgBr2 = Mg+2 Br1- = magnesium bromide

  50. Naming Binary Ionic Compounds pp • Problems with the transition metals, which can have more than one charge. • We need to figure out their charges. • The compound must be neutral. • Same number of (+) and (–) charges. • So, use the anion (-) to determine the charge on the positive ion. • Use a roman numeral with the cationto show the charge (not the subscript). • This is the stock system of nomenclature

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