Chemical Names and Formulas

1. Chemical Names and Formulas Chapter 9

2. Naming Ions Essential Question: How are the charges for Group A elements and for Transition elements determined?

3. Monatomic Ions • Monatomic ions consist of a single atom with a positive or negative charge. • Metals lose electrons to form cations • Non-metals gain electrons to form anions

4. Charges of Cations • Metals of Groups 1A, 2A and 3A lose electrons and form ions with charges equal to their group number. • The charge of any Group A nonmetal can be determine from the group number. • The charge on ions from transition metals must be determined from the number of electrons lost.

6. Charges of Anions • The charge of Group A anions can be determined by subtracting 8 from the Group number. • Ask yourself, “How many electrons must be gained to have the same number of electrons as a noble gas?”

12. Transition Metal Ions • Two methods are used to identify the transition metal ions: • The preferred method is the Stock System • An older, less useful method is the Classical System

13. The Stock System • A Roman numeral in parentheses is placed after the name of the element to indicate the strength of the charge. • Fe2+ is named the iron(II) ion • Fe3+ is named the iron(III) ion • Identify the names of the following ions: Cu+ Pb2+ Cr3+ Sn4+ Mn3+ Co2+

14. The Classical System • Uses a root word with different suffixes • The classical name is used to form the root name for the element (ferrum, plumbum, cuprum, etc.) • The suffix –ous is used to indicate the weaker of two charges. • The suffix –ic is used to indicate the stronger of two charges.

15. The Classical System (cont.) • For example, the lower charges for a few ions would be plumbous, cuprous, stannous, cobaltous, etc. • The higher of two charges would be plumbic, cupric, stannic, cobaltic, etc.

16. The Classical System (cont.) • What major disadvantages can you see in the Classical System? • The name does not tell you the actual charge on the ion. • It does not allow for elements that form more than two ions.

17. Can you name the following “compound?”

18. Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+

19. Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Ferrous wheel Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+ Fe2+

20. “Trustworthy” Transition Metals • A few transition metals have only one ionic charge. • The names of these cations do not have a Roman numeral in their names. • These “trustworthy” transition metals include Silver…………cadmium and zinc.

21. Polyatomic Ions • Some ions are composed of more than one atom. • These are called polyatomic ions. • Polyatomic ions are tightly bonded groups of atoms that behave as a single unit and carry a charge.

22. Examples of Polyatomic Ions

23. Polyatomic Ions • The name of most polyatomic ions ends in –ite or –ate. • There are important exceptions, including: • Ammonium (NH4+) • Cyanide (CN-) • Hydroxide (OH-)

24. Polyatomic Ions • Look for pairs of ions for which there is both an –ite and an –ate ending… • Note the number of oxygen atoms and the endings on each name… • You should be able to see a pattern… • The –ite ending indicates one fewer oxygen than the –ate ending.

25. Hydrogen-Containing Ions • Formulas beginning with H (hydrogen) have the H+ ion attached to an ion. • Notice the effect this has on the charge of the original ion. • H+ + CO32- results in HCO3-, for example.

30. Naming and Writing Formulas for Ionic Compounds Essential Question: How are the names of binary ionic compounds determined, and how do you write the formulas for the two types of ionic compounds?

31. Binary Ionic Compounds • Many ionic compounds have “common” names such as: Potash (K2CO3), baking soda (NaHCO3), laughing gas (N2O), plaster of paris (CaSO4 • 2H2O), epsom salt (MgSO4•7H2O), etc. • But a systematic way of naming compounds is essential to communication.

32. Naming Binary Ionic Compounds • A binary compound is composed of two elements, and can be either ionic or molecular. • The name of any binary ionic compound is the name of the cation followed by the name of the anion (which always ends in –ide).

33. Binary Ionic Compound Names • Name the following compounds: Cs2O NaBr SrF2 MgO K2S AlN Ca3P2 BaBr2 • Naming ionic compounds with transition metals presents a problem… FeO Fe2O3 CuF CuF2

34. Naming Ionic Compounds (cont.) • The preceding examples show that naming the ions of transition elements requires knowledge of the charge. • You can determine the strength of the charge by observing what the ion is bonded to.

35. Naming Ionic Compounds (cont.) • After determining the strength of the charge, the charge is identified using Roman numerals in parenthesis. • Try these examples: FeO Fe2O3 CuF CuF2 PbS PbF4 CoO CoI3

36. Naming Ionic Compounds With Polyatomic Ions • The name of any ionic compound is the name of the cation followed by the name of the anion. • Name the following compounds: Ca(OH)2 KCN NaMnO4 Li2SO4 Mg(C2H3O2)2 Mg(CH3COO)2 NiHCO3 Pb(SCN)2

37. Writing Formulas forIonic Compounds • Write the symbol for the cation followed by the symbol for the anion. • Add whatever subscripts are needed to balance the charges.

38. Writing Formulas forIonic Compounds • Consider using the “crisscross method” to identify the subscripts. • With this method the numerical value of the charge of each ion becomes the subscript for the other ion. • You must remember to reduce the values to the lowest ratio possible.

43. Compounds with Polyatomic Ions • Write the symbol for the metal ion followed by the formula for the polyatomic ion and balance the charges. • If there is more than one polyatomic ion in the formula, it must be enclosed in parenthesis before adding the subscript. • For example, Ca(NO3)2 and Mg(CN)2

48. Naming and Writing Formulas for Molecular Compounds Essential Question: What does a prefix in the name of a binary molecular compound indicate, and how do you write the formula for a binary molecular compound?

49. Naming BMC’s • Binary molecular compounds are composed to two elements, both of them non-metals. • With BMC ions are NOT involved, so FORGET THE CHARGES!!!!

50. Binary Molecular Compounds • When two non-metallic elements combine, they can do so in a variety of ways: NO NO2 N2O N2O2 N2O4 N2O5 • Prefixes in the name of BMCs tell how many atoms of each element are present in each molecule of the compound.