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Ch. 7 (Con’t.) Formula Writing & Naming of Compounds

Ch. 7 (Con’t.) Formula Writing & Naming of Compounds

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Ch. 7 (Con’t.) Formula Writing & Naming of Compounds

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  1. Ch. 7 (Con’t.)Formula Writing & Naming of Compounds

  2. Predicting Charges on Monatomic Ions KNOW THESE !!!! +1 +2 -3 -2 -1 0 Cd+2

  3. Chemical Formulas • Chemical formula- • Consists of element symbols and subscripts C6H12O6 • Formula Units – simplest whole # ratios of ions present in a compound (for ionic compounds) • Molecular Formulas- used for covalently bonded compounds. • (show EVERY atom present in a molecule) • Ex. H2O Water has 2 hydrogen atoms and 1 oxygen atom

  4. Writing Balanced Chemical Formulas Step 3: Example: Aluminum Chloride Criss-Cross Rule for Ionic Compounds Step 1: write symbols & charge of elements Cation (metal) always written 1st! Aluminum Chloride 1- Al Cl 3+ Step 2: criss-cross charges as subscripts Al Cl 1 3 AlCl3 combine as formula unit (“1” is never shown) (use smallest whole # ratio) Make sure you remove charges!!

  5. charge on cation “becomes” subscript of anion charge on anion “becomes” subscript of cation ** Warning: Reduce subscripts to lowest terms. Ones are not included in formulas!! Al3+ and O2– Ba2+ and S2– In3+ and Br1– Al2 O3 Ba2 S2 In1 Br3 Al2O3 BaS InBr3 aluminum oxide barium sulfide indium bromide

  6. Example: Magnesium Oxide Criss-Cross Rule Step 1: Magnesium Oxide Step 2: Mg2+ O2- Step 3: Mg O 2 2 Step 4: Mg2O2 Step 5: MgO

  7. Putting Ions Together Na+ + Cl- = NaCl Ca+2 + Cl- = CaCl2 Ca+2 + O-2= CaO Na+ + O-2 = Na2O Al+3 + S-2 = Al2S3 Ca+2 + N-3 = Ca3N2 You try these! Li+ + Br- = LiBr Mg+2 + F- = MgF2 Al+3 + I- = AlI3 K+ + Cl- = KCl Sr3P2 Sr+2 + P-3 =

  8. Crisscross • Switch the numerical value of the charges Ba2+ N3- 3 2 Ba3 N2 • Reduce ratio if possible

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

  10. Solution 1. Na+, S2- b) Na2S 2. Al3+, Cl- a) AlCl3 3. Mg2+, N3- c) Mg3N2

  11. Polyatomic Ions There are some ions that are made up of more than one type of atom, these are called Polyatomic ions – groups of covalently bonded atoms with a charge For example, the polyatomic ion known as ammonium NH4+ has 4 atoms of hydrogen and one atom of nitrogen, HOWEVER, the whole “group” has an overall charge of +1 ** you need to memorize the formulas & the charges of many polyatomic ions!

  12. Polyatomic Ions NO3- nitrate ion NO2- nitrite ion

  13. Naming Ternary Ionic Compounds • contain at least 3 elements & the 1st is a metal: • there MUST be at least onepolyatomic ion (it helps to circle the ions) • Examples: NaNO3Sodium nitrate K2SO4Potassium sulfate Al(HCO3)3Aluminumbicarbonate or Aluminumhydrogen carbonate

  14. What About. . . What if I have to put multiple polyatomic ions in a compound, for example, magnesium nitrate? Magnesium has a charge of +2 Nitrate is polyatomic ion and has a charge of -1 Therefore, we need 2 nitrate ions for each magnesium In this case, we put the entire polyatomic ion in parenthesis and put the subscript outside the parenthesis Our answer would be Mg(NO3)2

  15. NH4+ Cl- IONIC COMPOUNDSremember: they have oppositely-charged ions in a rigid 3-D pattern ammonium chloride, NH4Cl

  16. Ternary Ionic Nomenclature Sodium Sulfate Na+ and SO4-2 Na2SO4 Iron (III) hydroxide Fe+3 and OH- Fe(OH)3 Ammonium carbonate NH4+ and CO3–2 (NH4)2CO3

  17. Writing Formulas w/Polyatomic Ions Reminder! Parentheses are required only when you need more than one “bunch” of a particular polyatomic ion. Ba2 and SO42– BaSO4 barium sulfate Mg2+ and NO21– Mg(NO2)2 magnesium nitrite NH41+ and ClO31– NH4ClO3 ammonium chlorate Sn4+ and SO42– Sn(SO4)2 tin (IV) sulfate Fe3+ and Cr2O72– Fe2(Cr2O7)3 iron (III) dichromate NH41+ and N3– (NH4)3N ammonium nitride

  18. Learning Check 1. aluminum nitrate a) AlNO3 b) Al(NO)3 c) Al(NO3)3 2. copper(II) nitrate a) CuNO3 b) Cu(NO3)2 c) Cu2(NO3) 3. Iron (III) hydroxide a) FeOH b) Fe3OH c) Fe(OH)3 4. Tin(IV) hydroxide a) Sn(OH)4 b) Sn(OH)2 c) Sn4(OH)

  19. Many polyatomic ions with the same endings on their names have a different number of oxygen atoms attached to the central atom. • For example chlorate ClO3-1 sulfate SO4-2 phosphate PO4-3 acetate C2H3O2-1

  20. Polyatomic Ion: a group of atoms that stay together and have a single, overall charge.

  21. The table below shows the prefixes and suffixes that tell the number of oxygen atoms present in the negative ion. Salt metalpolyatomic ion # Oxygen atoms ________ per_____ate 1 more O ________ _____ate common ________ _____ite 1 less O ________ hypo_____ite 2 less O’s ________ _____ide 0 O’s

  22. The oxy-ions of chlorine & bromine all have these trends in common. Look for them below…… perchlorateClO4-1 chlorateClO3-1 chloriteClO2-1 Hypochlorite ClO-1 PerbromateBrO4-1 BromateBrO3-1 BromiteBrO2-1 HypobromiteBrO-1 The most productive method of committing these ions to memory is first memorize the ones that have the -ate ending. This is the most common ending.

  23. Practice Problem #2 sodium chlorite Choose the correct formula for the compound 1. NaCl No, you need to review prefixes 2.NaClO No, you need to review prefixes Very good, click arrow to continue 3. NaClO2 No, you have several errors 4. Na(ClO)2 No, there is a correct answer 5. none of the above nextproblem Prefixes Periodic Chart

  24. Naming Compounds What's in a name? That which we call a roseby any other name would smell as sweet."- William Shakespeare, Romeo and Juliet (II, ii)

  25. Naming Compounds Binary Ionic Compounds (metal & nonmetal): • 1. Cation first, then anion • 2. Monatomic cation = name of the element • Ca2+ = calcium ion • 3. Monatomic anion = root + -ide • Cl- = chloride • CaCl2 = calcium chloride

  26. Name these ions • Cl1- Chloride ion • N3- Nitride ion • Br1- Bromide ion Oxide ion • O2- Gallium ion • Ga3+

  27. Naming Binary Ionic Compounds • Examples: NaCl ZnI2 Al2O3 sodium chloride zinc iodide aluminum oxide

  28. Formulas to Names: Ternary Compounds 1. Write the names of the ions KMnO4 I’m a polyatomic ion potassium permanganate Final Name If the positive ion has a fixed charge, you are finished.

  29. Formulas to Names: Ternary Compounds 1. Write the names of the ions NH4NO3 I’m a polyatomic ion ammonium nitrate Final Name If the positive ion has a fixed charge, you are finished.

  30. Learning Check Match each set with the correct name: 1.Na2CO3a) magnesium sulfite MgSO3b) magnesium sulfate MgSO4c) sodium carbonate 2 . Ca(HCO3)2a) calcium carbonate CaCO3b) calcium phosphate Ca3(PO4)2 c) calcium bicarbonate

  31. Practice Naming Ionic Compounds Na2CO3 -- CaSO4 -- KBr -- MgS -- BeCl2 -- NH4F --

  32. Multiple Oxidation Numbers • When the metal in an ionic compound is multi-valent (has more than 1 charge) there are 2 naming methods: • Latin & Stock Systems • Latin is older (not useful for some compounds) • The metal is named with it’s Latin or English root and ends in -ic or –ous to denote charge. • E.g. Cu+1 is cuprous, E.g. Cu+2 is cupric • Lower = ous, Higher = ic

  33. Write the balanced formula for copper chloride & name it: Cu+2 + Cl-1 = CuCl2 = cupric chloride Cu+1 + Cl-1 = CuCl = cuprous chloride For Latin naming: know rules, possible charges, Latin names, & suffixes

  34. Examples of Older Names of Cations formed from Transition Metals

  35. Multiple valence: Stock System • The oxidation number (charge) of the metal is indicated in parentheses using Roman numerals • E.g. Cu1+ is copper(I), Cu2+ is copper(II) • Numbers refer to charges not to #s of atoms • Try: Cu2++Cl-1 & Cu1++Cl-1, • Cu+2++Cl-1 = CuCl2 = copper (II) chloride Cu+1 + Cl-1 = CuCl = copper (I) chloride

  36. Formula to Name:How do I figure out the Roman Numeral??Hint: We’ve already learned this! • 1) Assign the element with the unknown charge a charge of x • 2) Multiply the charge of each element by the number of atoms of that element to get the total charge. • 3) Add the products from step 2 and set them equal to zero because compounds are neutral- zero charge • 4) Solve for the unknown charge.

  37. Binary CompoundsContaining a Metal of Variable Oxidation Number To name these compounds, give the name of the metal (Type II cations) followed by Roman numerals in parentheses to indicate the oxidation number of the metal, followed by the name of the nonmetal, with its ending replaced by the suffix –ide. Examples Stock System Traditional (OLD) System (II) Iron chloride Ferrous chloride FeCl2 FeCl3 Iron chloride (III) Ferric chloride (II) SnO Tin oxide SnO2 Tin oxide Stannous oxide (IV) Stannic oxide (“ic” ending = higher oxidation state; “ous” is lower oxidation state)

  38. Ternary Ionic Nomenclature Writing Formulas • Write each ion, cation first. Don’t show charges in the final formula. • Overall charge must equal zero. • If charges cancel, just write symbols. • If not, use subscripts to balance charges. • Use parentheses to show more than one of a particular polyatomic ion. • Use Roman numerals indicate the ion’s charge when needed (Stock System)

  39. How do I figure out the Roman Numeral?

  40. Solving for the roman numeral (charge) of Fe2O3 • (2x) + (3)(-2) = 0 • # of Fe atoms times charge of Fe + number of O atoms times charge of O = zero because compounds are neutral, no charge • 2x + (-6) = 0 • 2x – 6 = 0 • 2x = 6 • x= 3 • Answer for the name: Iron (III) oxide

  41. Examples #6- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion Cu2S X = +1 2X + (-2) = 0 2Cux(S)-2= 0 I’m not a polyatomic ion copper sulfide (I) Final Name

  42. Examples #1- Formulas to Names 1. Write the names of the ions = 0 -2 CuSO3 2. Determine the charge of the positive ion Cu +2 SO3 x X + (- 2) = 0 I’m a polyatomic ion You must know the charge on the sulfite ion is -2 The sum of the positive and negative charges must equal zero +2 +2 X = +2 copper sulfite (II) Final Name Next

  43. Examples #4- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion SnF2 X = +2 X + 2(-1) = 0 Snx (F-1)2= 0 tin fluoride (II) Final Name

  44. X1 = Y3 Example #3-Names to Formulas 1. Write symbols of elements 3X = 1y nickel(III) acetate X(+3) + y(-1) = 0 2. Determine number of ions (Ni+3)x(C2H3O2-1)y= 0 Choose the lowest set of integers thatsatisfies the equation (C2H3O2)3 C2H3O2 Ni 1 Final Formula If there is only one atom the “1” is not shown Next

  45. Practice Problem #1 Fe(NO3)3 Choose the correct name for the compound 1. Iron trinitrate No, you do not use prefixes 2. iron(I) nitrate No, you have the wrong oxidation number 3. iron(III) nitrite No, you need to review polyatomic ions 4. iron(III) nitrate Very good, click arrow to continue 5. none of the above No, there is a correct answer nextproblem Periodic Chart Polyatomic Ions

  46. Learning Check Complete the names of the following binary compounds with variable metal ions: FeBr2 iron (_____) bromide CuCl copper (_____) chloride SnO2 ___(_____ ) ______________ Fe2O3 ________________________ Hg2S ________________________

  47. Nomenclaturefor molecular (Covalent) binary compounds (two nonmetals) • Uses a Prefix System • 1 .Less electronegative atom comes first. (towards left side of P.T.) • 2. Add numerical prefixes to indicate # of atoms of each element. 3. Change the ending of the second element to –ide (since it’s binary)

  48. In order to be effective in using prefixes to name compounds containing two non-metals, these prefixes must be committed to memory: mono- 1 hepta- 7 di- 2 octa- 8 tri- 3 nona- 9 tetra- 4 deca- 10 penta- 5 hexa- 6

  49. Naming covalent compounds • prefixrefersto#ofatoms-notcharge • N2O4 = dinitrogen tetroxide • Exception:don’t usemonoforfirstelement • CO2 = carbon dioxide • The first vowel is often dropped to avoid the combination of “ao” or “oo”. • CO=carbonmonoxide(monooxide) P4O10= tetraphosphorus decoxide (decaoxide)