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Objectives

Objectives. PSc.2.2.3 Predict chemical formulas and names for simple compounds based on knowledge of bond formation and naming conventions. Naming Compounds and Writing Formulas. Systematic Naming. There are too many compounds to remember the names of them all.

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Objectives

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  1. Objectives PSc.2.2.3 Predict chemical formulas and names for simple compounds based on knowledge of bond formation and naming conventions.

  2. Naming Compounds and Writing Formulas

  3. Systematic Naming • There are too many compounds to remember the names of them all. • A compound is made of two or more elements. • The name should tell us how many and what type of atoms.

  4. Types of Compounds • There are two types of compounds: ionic compounds and molecular (covalent) compounds.

  5. Ionic Compounds • The simplest ratio of the ions represented in an ionic compound is called a formula unit. • The overall charge of any formula unit is zero. • In order to write a correct formula unit, one must know the charge of each ion.

  6. Charges on Ions:Oxidation Numbers 1+ 2+ 3+ 3- 2- 1-

  7. Naming Cations • We will use the systematic way. • For cations, if the charge is always the same (Group A) just write the name of the metal.

  8. Naming Cations • Tin and lead can have more than one type of charge. • Indicate the charge with Roman numerals in parenthesis.

  9. Example • Li1+ • Li is the symbol for lithium. • Lithium is a Group 1A metal, so the charge is always the same. Write the name of the metal. • Li1+ is called the Lithium ion.

  10. Example • Sr2+ • Sr is the symbol for strontium. • Strontium is a Group 2A metal, so the charge is always the same. Write the name of the metal. • Sr2+ is called the Strontium ion.

  11. Example • Sn2+ • Sn is the symbol for tin. • Tin has multiple oxidation numbers. Write the name of the metal, indicating the charge with Roman numerals in parenthesis. • Sn2+ is called the Tin (II) ion.

  12. Example • Pb4+ • Pb is the symbol for lead. • Lead is a Group 4A metal, and the charge is not always the same. Write the name of the metal, indicating the charge with Roman numerals in parenthesis. • Pb4+ is called the Lead (IV) ion.

  13. Problem • Name the following cations. • Ca2+ Calcium ion Aluminum ion • Al3+ Tin (IV) ion • Sn4+

  14. Naming Anions • Naming monatomic anions is always the same. • Change the element ending to – ide • Example: F1- • F is the symbol for fluorine, F1- is fluor ide. ine.

  15. Example • Cl1- • Cl is the symbol for chlorine. • Chlorine is a Group 7A nonmetal, so the charge is always the same (1-). • Cl1- is called the chloride ion.

  16. Example • O2- • O is the symbol for oxygen. • Oxygen is a Group 6A nonmetal, so the charge is always the same (2-). • O2- is called the oxide ion.

  17. Problem • Name the following anions. • S2- sulfide ion • Br1- bromide ion • N3- nitride ion

  18. Problem • Name the following anions. • As3- arsenide ion • Te2- telluride ion

  19. Binary Ionic Compounds • Binaryionic compounds are composed of a metal bonded with a nonmetal. • Name the metal ion using a Roman numeral in parenthesis if necessary. • Follow this name with the name of the nonmetal ion.

  20. Example • Name the following binary ionic compounds. Sodium chloride • NaCl • Ca3P2 Calcium phosphide

  21. Example • Name the following binary ionic compounds. • PbO Lead (II) oxide • SnBr2 Tin (II) bromide

  22. Problem • Name the following binary ionic compounds. • PbO2 Lead (IV) oxide • AlF3 Aluminum fluoride

  23. Problem • Name the following binary ionic compounds. • KCl Potassium chloride • Na3N Sodium nitride

  24. Writing the Formulas for Cations • Write the formula for the metal. • If a Roman numeral is in parenthesis use that number for the charge. Indicate the charge with a superscript.

  25. Writing the Formulas for Cations • If no Roman numeral is given, find the Group A metal on the periodic table and determine the charge from the column number.

  26. Example • Lead (II) ion • Pb is the symbol for lead. • Lead has multiple charges, which is the reason why the charge with Roman numerals in parenthesis was included. • The formula for the lead (II) ion is Pb2+.

  27. Example • Gallium ion • Ga is the symbol for gallium. • Gallium is a Group 3A metal and its charge is always the same (3+). • The formula for the gallium ion is Ga3+.

  28. Problem • Write the formulas for the following cations. Mg2+ • Magnesium ion Cu2+ • Copper (II) ion • Potassium ion K1+

  29. Problem • Write the formulas for the following ions. Al3+ • Aluminum ion Cr6+ • Chromium (VI) ion Hg2+ • Mercury (II) ion

  30. Writing the Formulas for Anions • Write the formula for the nonmetal. • Find the Group A nonmetal on the periodic table and determine the charge from the column number.

  31. Problem • Write the formulas for the following anions. I1- • iodide ion P3- • phosphide ion

  32. Problem • Write the formulas for the following anions. • selenide ion Se2- • carbide ion C4-

  33. Ionic Compounds • Oxidation numbers can be used to determine the chemical formulas for ionic compounds. • If the oxidation number of each ion is multiplied by the number of that ion present in a formula unit, and then the results are added, the sum must be zero.

  34. Ionic Compounds • In the formula for an ionic compound, the symbol of the cation is written before that of the anion. • Subscripts, or small numbers written to the lower right of the chemical symbols, show the numbers of ions of each type present in a formula unit.

  35. Writing Formulas for Binary Ionic Compounds • Write the symbol for the metal. Determine the oxidation number from either the column number or the Roman numeral and write it as a superscript to the right of the metal’s symbol.

  36. Writing Formulas for Binary Ionic Compounds • To the right of the metal’s symbol, write the symbol for the nonmetal. Determine the oxidation number from the column number and write it as a superscript to the right of the nonmetal’s symbol.

  37. Writing Formulas for Binary Ionic Compounds • Example: potassium fluoride 1+ 1- K F

  38. Writing Formulas for Binary Ionic Compounds • If the two oxidation numbers add together to get zero, the formula is a one-to-one ratio of the elements.

  39. Writing Formulas for Binary Ionic Compounds • Example: potassium fluoride 1+ 1- K KF F

  40. Writing Formulas for Binary Ionic Compounds • Example: aluminum sulfide 3+ 2- Al S

  41. Writing Formulas for Binary Ionic Compounds • If the two oxidation numbers DO NOT add together to get zero, you will need to “criss-cross” the superscripts. These numbers now become subscripts.

  42. Writing Formulas for Binary Ionic Compounds • Example: aluminum sulfide 3+ 2- Al S 2- 3+

  43. Writing Formulas for Binary Ionic Compounds • Omit all positive and negative signs and omit all 1’s.

  44. Writing Formulas for Binary Ionic Compounds • Example: aluminum sulfide Al Al2S3 S 2 3

  45. Problem • Lithium selenide • Write the formulas for the following binary ionic compounds. Li2Se • Tin (II) oxide SnO

  46. Problem • Tin (IV) oxide • Write the formulas for the following binary ionic compounds. SnO2 • Magnesium fluoride MgF2

  47. Ternary Ionic Compounds • Ternaryionic compounds are composed of at least 3 elements. • Name the metal ion, using a Roman numeral in parenthesis if necessary. • Follow this name with the name of the polyatomic ion.

  48. Polyatomic ions • Polyatomic ions are groups of atoms that stay together and have a charge. • Examples include: • Nitrate NO3-1 • Acetate C2H3O2-1 • Hydroxide OH-1 • Ammonium NH4+1 • Carbonate CO3-2 • Sulfate SO4-2 • Phosphate PO4-3

  49. Ternary Ionic Compounds • There is one polyatomic ion with a positive oxidation number (NH4+) that may come first in a compound. Name the ion. • Follow this name with the name of the anion or second polyatomic ion.

  50. Examples • Name the following ternary ionic compounds. • Li2CO3 Lithium carbonate • Al(OH)3 Aluminum hydroxide

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