Comprehensive Guide to Naming and Writing Formulas for Ionic and Molecular Compounds

1. Chapter 5 Naming Compounds Writing Formulas

2. 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

3. 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.

4. 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

5. 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 • 2 Fe must = +6, so each is +3. • iron (III) oxide

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

7. Ternary Ionic Compounds • Will have polyatomic ions • At least three elements • Just write the name of the element using the front of the periodic table and the polyatomic ion using the chart on the back of the table. • Examples of naming ternary ionic compounds: • NaNO3 = sodium nitrate • (NH4)2O = ammonium oxide

8. Ternary Ionic Compoundsname these: • LiCN • Fe(OH)3 • (NH4)2CO3 • NiPO4 • CaSO4 • CuSO3

9. Writing Formulas • The charges have to add up to zero. • Get charges for the 2 parts. • Cations from location on p. table. • Anions from p. table or polyatomic. • Balance the charges by putting in subscripts (small #’s on bottom right). • Put polyatomic ions in parenthesis before you give them subscripts.

10. 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 Cl2-1 • CaCl2

11. 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

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

13. Things to look for • If cations have (roman numeral), the number is their charge. • If anions end in -ide they are probably off the periodic table (Monoatomic) • Exceptions (Hydroxide (OH); Cyanide (CN) are polyatomic. • If anion ends in -ate or -ite it is polyatomic.

14. Molecular Compounds Writing names and Formulas

15. 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

16. 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 kind of atoms. • Uses prefixes to tell you the number

17. Prefixes • 1 mono- • 2 di- • 3 tri- • 4 tetra- • 5 penta- • 6 hexa- • 7 hepta- • 8 octa- • 9 nona- • 10 deca-

18. Prefixes • To write the name write two words Prefix name Prefix name -ide

19. Prefixes • To write the name write two words • One exception is we don’t write mono- if there is only one of the first element. Prefix name Prefix name -ide

20. Prefixes • 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) Prefix name Prefix name -ide

21. Ex. CO carbon monoxide CO2 carbon dioxide P2O5 diphosphorus pentoxide Name These • N2O • NO2 • Cl2O7 • CBr4 • BaCl2

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

23. Acids Writing names and Formulas

24. 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.

25. 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

26. Naming Acids • If the anion has oxygen in it • it ends in -ate or -ite • change the suffix -ate to -ic acid • HNO3 Hydrogen and nitrate ions • Nitric acid • change the suffix -ite to -ous acid • HNO2 Hydrogen and nitrite ions • Nitrous acid

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

28. Writing Acid Formulas/Naming • Hydrogen will always be first • name will tell you the anion • make the charges cancel out • Starts with hydro- if no oxygen in the acid, -ide ending becomes –ic Ex. HCl = hydochloric acid • no hydro, -ate ending from polyatomic ion becomes -ic, H2SO4 = sulfuric acid -ite ending becomes –ous, H2SO3 = sulfurous acid

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