An Introduction to Chemical Nomenclature ( What s in a name? )

Transcription

1 An Introduction to Chemical Nomenclature ( What s in a name? ) Model 1 The Periodic Table of the Elements and some Chemical Compounds Chemical Formula NaCl CaS Al 2 O 3 Zn 3 P 2 CO CO 2 NO N 2 O Type of Compound Critical Thinking Questions. 1. What are the three types of elements that are shown in the periodic table? 2. What types of elements appear to make up ionic compounds? 3. What types of elements appear to make up covalent compounds?

2 Model 2 Some Compounds Compound CO CO 2 NO N 2 O P 5 O 10 Name carbon monoxide carbon dioxide nitrogen monoxide dinitrogen monoxide pentaphosphorous decoxide Critical Thinking Questions 4. Do the names of these compounds tell you how many of each type of atom there are in the compound? Explain. 5. Ammonia is the common name for the compound NH 3. What is the systematic name of the compound? 6. Based on the information in the model, what can you say in general about the names of compounds like these? (In other words, can you suggest a general way to name these types of compounds?) Information The following table lists some of the common prefixes. Number of atoms Prefix Number of atoms Prefix 1 mono 6 hexa 2 di 7 hepta 3 tri 8 octa 4 tetra 9 nona 5 penta 10 deca There is a nomenclature tree on the CHEM 210 website. You should practice using it so you can name compounds. You will be responsible for being able to use chemical nomenclature in this class and in lab.

3 Model 3 Some Compounds Formula Name Cation (name) Anion (name) NaCl sodium chloride Na + (sodium ion) Cl - (chloride ion) Al 2 O 3 aluminum oxide Al 3+ (aluminum ion) O 2- (oxide ion) Cu 2 SO 4 copper(i) sulfate (or cuprous sulfate - archaic) Cu + (copper(i) ion) 2- SO 4 (sulfate ion) CuSO 3 copper(ii) sulfite (or cupric sulfite - archaic ) Cu 2+ (copper(ii) ion) 2- SO 3 (sulfite ion) NH 4 NO 3 Ammonium nitrate + NH 4 (ammonium ion) - NO 3 (nitrate ion) Fe 3 P 2 Iron(II) phosphide (or ferrous sulfide - archaic) Fe 2+ (Iron(II) ion) P 3- (phosphide ion) FeP Iron(III) phosphide (or ferric sulfide - archaic) Fe 3+ (Iron(III) ion) P 3- (phosphide ion) Critical Thinking Questions 7. What is the difference between a cation and an anion? 8. What is listed first in the formula and name of an ionic compound, the anion or the cation? 9. Suggest a general way to name ionic compounds from the information in the model. 10. Based on what you know from the table, what do you think the name of NaF is? 11. Can ions be polyatomic (more than one atom, which would be monatomic)? 12. How does a name tell you the charge of a cation? 13. If NO 3 is the nitrate ion, what do you think is the name of NO 2? 14. How do you determine the relative number of cations and anions in the compound?

4 Information. There is a list of ions, acids and bases with their names and formulas on the CHEM 210 webpage: You need to memorize all of these. Model 4 Acid nomenclature A family of covalent compounds can break up into ionic species when dissolved in water because of its ability to donate a hydrogen ion to the surrounding water molecules. In order to reflect this reaction, the compound is often given two names one for the molecular species and a second name for the dissolved compound. The names follow systematic rules. The family has two branches: binary (hydrogen + one other element) and polyatomic acids. Model 4A: Binary Acid: HCl(g) + nh 2 O(l) HCl(aq) H + (aq) + Cl (aq) hydrogen chloride gas water hydrochloric acid hydrogen ion 15. Compare the names of HCl(g) and HCl(aq); what are the differences? chloride ion 16. Compare the names of HCl(aq) and Cl (aq); write a general rule for the naming the acid species from the name of the anion formed. 17. Using the information from the previous question, name the following set of compounds: Na 2 S, H 2 S(g) and H 2 S(aq)

5 Model 4B: Polyatomic Acid: HC 2 H 3 O 2 (aq) H + (aq) + C 2 H 3 O 2 (aq) acetic acid hydrogen ion acetate ion 18. Compare the names of HC 2 H 3 O 2 (aq) and C 2 H 3 O 2 (aq); write a general rule for the naming the acid species from the name of the anion formed. Acid Sodium salt Formula Name Formula Name H 2 S hydrosulfuric acid Na 2 S sodium sulfide H 2 SO 4 sulfuric acid Na 2 SO 4 sodium sulfate H 2 SO 3 sulfurous acid Na 2 SO 3 sodium sulfite 19. Given this set of acids, how would you modify your rule for naming acids? 20. Using your rule, how would you name H 3 PO 4 (aq) and H 3 PO 3 (aq)? A partial list of acids and the sodium salts: Acid Sodium salt Formula Name Formula Name HCl hydrochloric acid NaCl sodium chloride HClO 3 chloric acid NaClO 3 sodium chlorate HClO 2 chlorous acid NaClO 2 sodium chlorite HClO 4 perchloric acid NaClO 4 sodium perchlorate HOCl hypochlorous acid NaOCl sodium hypochlorite H 2 S hydrosulfuric acid Na 2 S sodium sulfide H 2 SO 4 sulfuric acid Na 2 SO 4 sodium sulfate H 2 SO 3 sulfurous acid Na 2 SO 3 sodium sulfite 21. Do you need to modify your rule for naming acids from the anion?

6 Model 4C: Monoprotic and polyprotic acids Many acids have more than one ionizable hydrogen atom and are known as polyprotic acids (i.e., H + proton ). Not all hydrogens are ionizable acetic acid (formula: HC 2 H 3 O 2 or CH 3 CO 2 H) has four hydrogen atoms, but is monoprotic. Example of polyprotic acid reactions: H 2 SO 3 (aq) HSO 3 (aq) + H + (aq) sulfurous acid hydrogen sulfite ion (or bisulfite) HSO 3 (aq) SO 3 2 (aq) + H + (aq) hydrogen sulfite ion (or bisulfite) sulfite ion The loss of the protons occur sequentially: it is always easier to remove the first proton from a polyprotic acid than to remove the second. 22. Write the set of reactions for the triprotic H 3 PO 4 (aq) and name all species in each reaction. Exercises 1. Provide the name or formula of each of the following ionic compounds: a. KBr b. AlF 3 c. BaO d. lithium oxide e. copper(ii) sulfide f. sodium phosphate 2. Provide the name or molecular formula of each of the following covalent compounds: a. sulfur hexafluoride b. arsenic trihydride c. carbon disulfide d. ICl 5 e. N 2 O 5 f. SiF 4 3. Identify each of the following as ionic or covalent compounds, and provide their formula or name. a. silver sulfate b. Hg 2 (NO 3 ) 2 c. SO 2 d. dihydrogen monoxide e. potassium phosphide f. Mg(OH) 2 4. Provide the name or the formula of each of the following acids. a. H 2 Se b. Hydrobromic acid c. carbonic acid d. HIO 4 e. bicarbonate ion f. H 2 PO 3 (aq)