Naming Compounds and Writing Formulas

1. Naming Compounds and Writing Formulas Unit 7, Part B

2. Valence Electrons as Electron Dots Remember that the number of valence electrons is a periodic trend! H He Li• •Be• •B• C N O F Ne • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

3. Atoms vs. Molecules vs. Ions Remember how to tell these apart! Atom: Single particle, pure element Example: Fe, C, Mg Molecule: Two or more nonmetal particles covalently bonded together Example: N2, CO2, H2O Ion: Charged atom or molecule Example: Cl-1, Zn+2, SO4-2

4. Group I: Binary Ionic Compounds with Metals of Fixed Charge This includes the metals from groups 1A (alkali metals are +1), 2A (alkaline earth metals are always +2), Al+3, Zn+2, and Ag+1. These metals will always have the same charge.

5. Binary Ionic Compound Formulas • Remember that in an ionic compound the charges must balance so that the compound is neutral • (The charge of the first atom multiplied by the subscript) + (the charge of the second atom multiplied by its subscript) must= 0 Na+ + Cl- NaCl

6. Binary Ionic Compound w/ Fixed Charge Naming • Write the name of the metal • Write the root of nonmetal + -ide suffix Formulas • Write the symbols for each element and their charges from the periodic table. • Crisscross the charges to get the subscripts. • Reduce to lowest terms

7. Binary Ionic Compound Formulas The Long Way • Find the least common multiple (LCM) of the ions’ charges • Multiply the charges by whatever number is needed to equal the LCM • That number will be your subscripts • Example: calcium phosphide Ca is +2 P is -3 Multiples of 2: 2 4 6 8 10 12 etc. Multiples of 3: 3 6 9 12 15 18 etc. 3 Ca3P2 For Ca +2 x ____ = +6 For P -3 x ____ = -6 2

8. Binary Ionic Compound Formulas Shortcut Criss-cross method! • Naming • Write the name of the metal • Write the root of nonmetal + -ide suffix • Crisscross the charges to get the subscripts. • Reduce to lowest terms • Calcium phosphide Note: You do not have to write a subscript of 1, just write the symbol. Also, reduce common numbers: Instead of Mg2O2, you just use MgO Ca3P2 CaP 3- 2 3 2+

9. Let’s try a few… • sodium chloride • barium bromide • aluminum oxide Na+1, Cl-1, so NaCl Ba+2, Br-1, so BaBr2 Al+3, O-2, so Al2O3 Remember, 1 is understood, so omit it!

10. Naming Binary Ionic Compounds • The positive ion (cation) goes first, and the negative ion (anion) goes second. • Use the name of the cation + the root name of the anion + the suffix –ide • Example: BaF2 Ba is barium F is fluorine barium fluoride

11. Let’s try a few… • Li3N • CaF2 • SrI2

12. Group 2: Binary Ionic Compounds with Metals That Vary in Charge These compounds use all the rest of the metals including transition metals. The charge on these metals could be anything between +1 and +7, depending on the metal, but two charges are most common for each.

13. Group 2: Ionic Compound w/ Transition Metals Naming • Write name of metal and its charge in Roman Numerals. • Write name of polyatomic ion, or nonmetal + -ide. Formulas • Write symbols for positive metal w/ charge + nonmetal or polyatomic ion w/ charge. • Crisscross charges for subscripts. If you need a subscript on a polyatomic ion, put parentheses around it first. • Reduce subscripts to lowest terms.

14. Formulas for Group 2 Criss-cross method • Write the charges for each ion. The metal charge is given in Roman Numerals! • Criss-cross the charges down as subscripts and reduce to lowest terms • Example: Copper (II) chloride CuCl2

15. Let’s try a few! • Lead (IV) oxide • Iron (II) sulfide • Iron (III) sulfide

16. Naming Group 2 Compounds • Name the metal first, and give its charge in Roman Numerals in parentheses. You can reverse criss-cross, or use the nonmetal charge to balance the positive. • Name the nonmetal root + -ide suffix. • Example: CrF2 Chromium (II) fluoride Remember!! The Roman Numeral is NOT the subscript!

17. Let’s try some! • CuBr2 • CuBr • SnO2

18. Polyatomic Ions • Many ionic compounds contain polyatomic ions, which are ions made up of more than one atom. • The charge given to the polyatomic ion applies to the entire group of atoms. Note that ammonium is the only positive polyatomic ion (cation).

19. Group 3: Ionic Compounds w/ Polyatomic Ions Naming • Write name of metal or + polyatomic ion, use RN as needed. • Write name of negative polyatomic ion or nonmetal + -ide. Formulas • Write symbols for positive ions and negative ions w/ charges. • Crisscross charges for subscripts. If you need a subscript on a polyatomic ion, put parentheses around it first. • Reduce subscripts to lowest terms.

20. Group 3: Writing Formulas with Polyatomic Ions • Follow the same rules as binary ionic compounds • Treat the polyatomic ion as a single unit; don’t change its subscripts • If more than one polyatomic ion is needed, place parentheses around it and write the subscript outside of the parentheses. Example: 2 carbonates is (CO32-)2

21. Writing Formulas with Polyatomic Ions • Example: magnesium chlorate magnesium is Mg charge is 2+ chlorate is ClO3- charge is 1- MgClO3 Mg(ClO3)2 - 2+ 1 2

22. Practice! • sodium nitrate • calcium chlorate • aluminum carbonate • potassium chromate

23. Group 3: Naming Compounds • Name the metal or positive polyatomic ion. Use Roman Numeral if needed for metal of varying charge. • Name the negative polyatomic ion, or nonmetal root + -ide suffix. • Example: Ca3(PO4)2 Calcium phosphate • Example: Cu(NO3)2 Copper (II) nitrate

24. Practice! • CaSO4 • Al(OH)3 • Pb(C2H3O2)4

25. Group 4: Binary Covalent Compounds Naming • Write the name of the first nonmetal. Put a prefix on it if it has a subscript. • Write a prefix for the second nonmetal + root of nonmetal + -ide. Formulas • Write the symbols of each nonmetal. • Use the prefixes to determine the subscript. Never use charges!!

26. PREFIXES • mono- • di- • tri- • tetra- • penta- • hexa- • hepta- • octa- • nona- • deca- Group 4: Naming Binary Covalent Compounds • Rules are similar to binary ionic compounds • Use the name of the first element • Use the root of the name of the 2nd element, plus the suffix –ide • But add prefixes to indicate the number of atoms in the compound Note: You do not have to say “mono-” for the first element. Example: CO is “carbon monoxide.”

27. PREFIXES • mono- • di- • tri- • tetra- • penta- • hexa- • hepta • octa- • nona- • deca- Naming Binary Covalent Compounds • NO2 • N2O5 Let’s try a few…

28. Naming Acids - Types • Binary acid: contains hydrogen and one other element • Examples: HCl, HBr • Oxyacid: contains hydrogen and an oxyanion, which is a polyatomic ion that contains oxygen • Examples: H2SO4, HNO3

29. Naming Binary Acids • Use the prefix hydro-to name the hydrogen part of the compound • Use the root of the 2nd element plus the suffix –ic • Add the word acid Example: HBr is hydrobromic acid

30. Practice Naming Binary Acids • HF • HCl • HCN (tricky!) • Some “binary” acids contain polyatomic ions • As long as there is NO OXYGEN, follow the regular binary acid rules • Hydro- + (root of ion) + -ic+ acid • So HCN would be… Hydrocyanic acid

31. Naming Oxyacids • Do NOT put hydro- • Identify the polyatomic anion present • Use the root of the anion’s name • Change the suffix • -ate –ic • -ite–ous • Add the word acid Example: H2SO4 contains sulfate… sulfuric acid

32. Practice with Oxyacids • H3PO4 • HNO2 • Sulfurous acid • Nitric acid