Understanding the Nomenclature of Binary Compounds and Polyatomic Ions

1. Nomenclature Chapter 4

2. Nomenclature = Naming • Common names were created before there was a system in place • More than 4 million chemical compounds, memorizing names would be impossible • A system makes it much easier

3. Binary Compounds • Compounds composed of 2 elements • 2 types • Metal and Nonmetal • Two Nonmetals

4. 4.1 Naming Compounds That Contain a Metal and a Nonmetal • Remember: When metals and nonmetals combine the compound contains ions • Resulting substance is a binary ionic compound • Contain cation and anion in that order • To name them simply name ions • Cation is element name • Anion is root of element name with –ide at end • NaCl is sodium chloride

5. Certain metal ions form only one cation • Na is always Na+ • Cs is always Cs+ • Ca is always Ca2+ • We will call these Type I cations and they form Type I binary compounds • Other metal ions can form more than one cation • Cr can form Cr2+ or Cr3+ • Lower oxidation number will end in –ous • Higher oxidation number will end in -ic • We will call these Type II cations and they form Type II binary compounds

6. Type I Binary Ionic Compounds • Cation always named first, anion second • When a single element is the cation we simply use its name • When a single element is the anion take the root and add –ide • Examples • NaI is sodium iodide • CaO is calcium oxide • What would KI be? Potassium iodide • What would CsBr be? Cesium bromide • Do Practice problems on page 87

7. Type II Binary Ionic Compounds • Need to specify which cation is used • Is it Cr2+ or Cr3+? • We will use Roman Numerals in name • So if it is FeCl2 which Iron is it? Fe2+ (the ferrous ion) or Fe3+ (the ferric ion)? • we know Chlorine has a 1- oxidation number so 2 (1-) = 2-, what must Fe be to cancel this out? • Fe must be 2+ so it is Fe2+ • So name would be Iron II chloride • Table 4.2 page 90

8. 4.2 Binary Compounds That Contain Only Nonmetals (Type III) • Write first element • Write second element • Add prefix to 1st element (but not mono-) • Add prefix to 2nd element • Why do we do this? • NO, N2O5, and NO2 would all be nitrogen oxide under the normal rules • Instead they are Nitrogen monoxide, Dinitrogen pentoxide, and Nitrogen dioxide • one –mono • two - di • three - tri • four - tetra • five - penta • six - hexa • seven - hepta • eight - octa • nine - nona • ten - deca

9. 4.3 Review • Type I • metal and nonmetal • Metal cation has only 1 oxidation number • Type II • Metal and nonmetal • Metal cation has more than 1 oxidation number • Tell which ox. # it is with roman numerals • Type III • Nonmetal and nonmetal • Use prefixes to name

10. Naming Binary Compounds

11. 4.4 naming Compounds That Contain Polyatomic Ions • FIRST: Copy Table 4.4 on page 100 into notes • Polyatomic ion – a charged group of atoms bound together • Oxyanion – oxygen and another element • Smallest – hypo- • Lower - -ite (If only 2, smallest) • Higher - - ate (If only 2, largest) • Largest – hyper

12. When naming compounds with polyatomic ions follow same rules but anion (second part of formula) is a polyatomic ion just name it

13. 4.5 Naming Acids • Acid – produces H+ ions (protons) in water • Tastes sour (not a good test) • It is like a molecule with a H+ attached to an anion • If no oxygen • Hydro- in front, -ic at end • HCl is Hydrochloric acid • If oxygen • Root of central element of anion or anion name with –ic or –ous • Anion ends in –ate then replace with –ic • Anion ends with –ite then replace with -ous

14. 4.6 Writing Formulas From Names • You know how to do this