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Representing Chemical Compounds

Representing Chemical Compounds. Naming Compounds and Writing Chemical Formulas. Chemical Formula. Shows the kinds and numbers of atoms in a substance. If only one atom of the element in a compound, you only write the element’s symbol. (Ex: Lithium fluoride  LiF)

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Representing Chemical Compounds

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  1. Representing Chemical Compounds Naming Compounds and Writing Chemical Formulas

  2. Chemical Formula • Shows the kinds and numbers of atoms in a substance. • If only one atom of the element in a compound, you only write the element’s symbol. (Ex: Lithium fluoride  LiF) • If the molecules of the element each have more than one atom, a number is used as a subscript. (Ex: Lithium oxide  Li2O).

  3. Molecular Formulas • Chemical formula for a molecular compound is called a molecular formula. • Shows the kinds and numbers of atoms present in a molecule of a compound. • Examples: CO, CO2 • Tells nothing about the structure of the molecule --- doesn’t show arrangement of the various atoms.

  4. Formula Units • Chemical formulas represent ionic compounds. • Formula units – lowest whole-number ratio of ions in the compound.

  5. Ionic Charges • For most of the Group A elements, the Periodic Table can tell what kind of ion they will form from their location. • Elements in the same group have similar properties. • Including the charge when they are ions.

  6. +1 +2 +3 -3 -2 -1

  7. Naming Cations • Cation- if the charge is always the same (Group A) just write the name of the metal. • Transition metals can have more than one type of charge. • Indicate the charge with roman numerals in parentheses.

  8. Name These • Na+1 • Ca+1 • Al+3 • Fe+3 • Fe+2 • Pb+3 • Li+1

  9. Write Formulas for these • Potassium ion • Magnesium ion • Copper (II) ion • Chromium (VI) ion • Barium ion • Mercury (II) ion

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

  11. Name These • N-3 • Br-1 • O-2 • Ga+3

  12. Write These • Sulfide ion • iodide ion • phosphide ion • Strontium ion

  13. Polyatomic Ions • Groups of atoms that stay together and have a charge.

  14. Ions in Ionic Compounds

  15. Naming Binary Ionic Compounds • 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 • NaCl = Na+ Cl- = sodium chloride • MgBr2 = Mg+2 Br- = magnesium bromide

  16. Naming Binary Ionic Compounds • The problem comes with the transition metals. • Need to figure out their charges. • The compound must be neutral. • same number of + and – charges. • Use the anion to determine the charge on the positive ion.

  17. Naming Binary Ionic Compounds • Write the name of CuO • Need the charge of Cu • O is -2 • copper must be +2 • Copper (II) chloride • Name CoCl3 • Cl is -1 and there are three of them = -3 • Co must be +3 Cobalt (III) chloride

  18. Naming Binary Ionic Compounds • Write the name of Cu2S. • Since S is -2, the Cu2 must be +2, so each one is +1. • copper (I) sulfide • Fe2O3 • Each O is -2 3 x -2 = -6 • 3 Fe must = +6, so each is +2. • iron (III) oxide

  19. Naming Binary Ionic Compounds • Write the names of the following • KCl • Na3N • CrN • Sc3P2 • PbO • PbO2 • Na2Se

  20. Ternary Ionic Compounds • Will have polyatomic ions • At least three elements • name the ions • NaNO3 • CaSO4 • CuSO3 • (NH4)2O

  21. Ternary Ionic Compounds • LiCN • Fe(OH)3 • (NH4)2CO3 • NiPO4

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

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

  24. Write the formulas for these • Lithium sulfide • tin (II) oxide • tin (IV) oxide • Magnesium fluoride • Copper (II) sulfate • Iron (III) phosphide • gallium nitrate • Iron (III) sulfide

  25. Write the formulas for these • Ammonium chloride • ammonium sulfide • barium nitrate

  26. Things to look for • If cations have (), the number is their charge. • If anions end in -ide they are probably off the periodic table (Monoatomic) • If anion ends in -ate or -ite it is polyatomic

  27. Molecular Compounds Writing names and Formulas

  28. Molecular compounds • made of just nonmetals • smallest piece is a molecule • can’t be held together because of opposite charges. • can’t use charges to figure out how many of each atom

  29. Easier Ionic compounds use charges to determine how many of each. • Have to figure out charges. • Have to figure out numbers. • Molecular compounds name tells you the number of atoms. • Uses prefixes to tell you the number

  30. Prefixes • 1 mono- • 2 di- • 3 tri- • 4 tetra- • 5 penta- • 6 hexa- • 7 hepta- • 8 octa-

  31. Prefixes • 9 nona- • 10 deca- • To write the name write two words

  32. Prefixes • 9 nona- • 10 deca- • To write the name write two words • Prefix name Prefix name -ide

  33. Prefixes • 9 nona- • 10 deca- • To write the name write two words • One exception is we don’t write mono- if there is only one of the first element.

  34. Prefixes • 9 nona- • 10 deca- • To write the name write two words • One exception is we don’t write mono- if there is only one of the first element. • No double vowels when writing names (oa oo)

  35. Name These • N2O • NO2 • Cl2O7 • CBr4 • CO2 • BaCl2

  36. Write formulas for these • diphosphorus pentoxide • tetraiodide nonoxide • sulfur hexaflouride • nitrogen trioxide • Carbon tetrahydride • phosphorus trifluoride • aluminum chloride

  37. Acids Writing names and Formulas

  38. Acids • Compounds that give off hydrogen ions when dissolved in water. • Must have H in them. • will always be some H next to an anion. • The anion determines the name.

  39. Naming acids • If the anion attached to hydrogen is ends in -ide, put the prefix hydro- and change -ide to -ic acid • HCl - hydrogen ion and chloride ion • hydrochloric acid • H2S hydrogen ion and sulfide ion • hydrosulfuric acid

  40. Naming Acids • If the anion has oxygen in it • it ends in -ate of -ite • change the suffix -ate to -icacid • HNO3 Hydrogen and nitrate ions • Nitricacid • change the suffix -ite to -ous acid • HNO2 Hydrogen and nitrite ions • Nitrousacid

  41. Name these • HF • H3P • H2SO4 • H2SO3 • HCN • H2CrO4

  42. Writing Formulas • Hydrogen will always be first • name will tell you the anion • make the charges cancel out. • Starts with hydro- no oxygen, -ide • no hydro, -ate comes from -ic, -ite comes from -ous

  43. Write formulas for these • hydroiodic acid • acetic acid • carbonic acid • phosphorous acid • hydrobromic acid

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