Honors Chemistry Unit 4 – Chemical Names & Formulas

1. Honors ChemistryUnit 4 – Chemical Names & Formulas Lesson 2 – Polyatomic Ions Book Section: 7-1 Objective: SWBAT generate formulas and name compounds with polyatomic ions. Do Now: Prepare for Quiz 4-1.

2. Polyatomic Ions • Some ions are made up of multiple atoms, these are called polyatomic ions. • You do not yet have the skills necessary to understand how they are assembled (you will!), so for now, you must memorize the twelve most common ions. Any others, I will provide to you.

3. Memorization List • Nitrate: NO3- • Sulfate: SO42- • Phosphate: PO43- • Hydroxide: OH- • Acetate: C2H3O2- • Ammonium: NH4+ • Chromate: CrO42- • Dichromate: Cr2O72- • Carbonate: CO32- • Cyanide: CN- • Iodate: IO3- • Bromate: BrO3- These are the ions that I will not provide to you. It is my strong recommendation that you take the time to actually memorize them by heart, especially if you have any hope of taking further physical science classes (physics, AP chem, etc.)

4. Names & Formulas With Polyatomics • Sodium acetate • Procedure is the same – balance charges with ions • Sodium: Na+ • Acetate: C2H3O2- • NaC2H3O2

5. Names & Formulas With Polyatomics • Magnesium nitrate • Magnesium: Mg+2 • Nitrate: NO3- • If you need multiple polyatomic ions, enclose the polyatomic ion in parentheses before you add the new subscript. • Mg(NO3)2

6. Practice • Give the names of the following: • Na2SO4 • (NH4)3P • Al(NO3)3 • Give the formulas for the following: • Potassium chromate • Calcium carbonate • Aluminum bromate

7. Patterns in Names • The reason you need to memorize the “ate” endings (nitrate, phosphate, etc.), is that many other ions can be found from them. • Most of these ions are called oxyanions (anions containing oxygen).

8. Oxyanions (2 varieties) • When there are two oxyanions involving the same element: • The one with more oxygens ends in –ate. • NO3- : nitrate SO42-: sulfate • The one with less oxygens ends in –ite. • NO2-: nitrite SO32-: sulfite

9. Oxyanions (4 varieties) • There are four versions of chlorine oxyanions: • ClO- • ClO2- • ClO3- • ClO4-

10. Oxyanions (4 varieties) • Start with the common “ate” • ClO- • ClO2- • ClO3-: chlorate • ClO4-

11. Oxyanions (4 varieties) • One less oxygen is “ite” • ClO- • ClO2- : chlorite • ClO3-: chlorate • ClO4-

12. Oxyanions (4 varieties) • One more oxygen adds “per” • ClO- • ClO2- : chlorite • ClO3-: chlorate • ClO4- : perchlorate

13. Oxyanions (4 varieties) • Two less oxygen adds “hypo” • ClO- : hypochlorite • ClO2- : chlorite • ClO3-: chlorate • ClO4- : perchlorate • These rules apply to reading and writing all oxyanions. Start with “ate” and move from there.

14. Transition Metals • Elements in the d-block are referred to as the transition metals. • This is because they can have multiple different charges. • In a compound’s name, we need to find a way to distinguish between different d-block charges.

15. Transition Metals • Example: Iron can either be +2 or +3 • So, there could be two types of iron oxide. • Fe+2 + O-2 = FeO • Fe+3 + O-2 = Fe2O3 • A Roman numeral is used to distinguish one from the other. • FeO = iron (II) oxide • Fe2O3 = iron (III) oxide • The Roman number is the charge on the transition metal.

16. Memorize This, Part 2 • There are four transition metals that only have one charge, and do not require Roman numerals. • Silver: Ag+ • Scandium: Sc2+ • Zinc: Zn2+ • Cadmium: Cd2+

17. More Practice • Name the following compounds: • Fe(NO3)3 • NaNO2 • Zn(ClO4)2 • Give the formula for the following compounds: • Sodium hypochlorite • Silver nitrate • Ammonium sulfite

18. Homework: #2-25 • This week: • Friday: Binary Molecular Compounds, Quiz 4-2 • Monday: Mole Day Celebration!