Nomenclature of Inorganic Compounds

Transcription

1 Nomenclature of Inorganic Compounds Chapter 6 Hein and Arena Version 1.1 Eugene Passer Chemistry Department Bronx Community 1 College John Wiley and Sons, Inc

2 Elements and Ions 2

3 The formula for most elements is the symbol of the element. Sodium Potassium Zinc Argon Mercury Lead Calcium Na K Zn Ar Hg Pb Ca 3

4 These 7 elements are found in nature as diatomic molecules. Hydrogen H 2 Nitrogen N 2 Oxygen O 2 Fluorine F 2 Chlorine Cl 2 Bromine Br 2 Iodine I 2 4

5 Formation of Ions 5

6 Positive Ion Formation: Loss of an Electron(s) From a Neutral Atom Na Na + + e - Ca Ca e - Al Al e - 6

7 Naming Cations 7

8 Cations are named the same as their parent atoms. 8

9 Atom sodium (Na) Cation Na + Name of Cation sodium ion 9

10 Atom calcium (Ca) Cation Ca 2+ Name of Cation calcium ion 10

11 Negative Ion Formation: Gain of an Electron(s) by a Neutral Atom Cl + e - Cl - O + 2e - O 2- N + 3e - N 3-11

12 Naming Anions 12

13 A monatomic anion consists of one element and has the stem of the parent element name with an ide ending 13

14 Atom fluorine (F) Anion F - stem Name of Anion fluoride ion 14

15 Atom oxygen (O) Anion O 2- stem Name of Anion oxide ion 15

16 Ions are always formed by adding or removing one or more electrons to or from a neutral atom. 16

17 Most often ions are formed when metals combine with nonmetals to form ionic solids with ionic bonds. 17

18 The charge on an ion can be predicted from its position in the periodic table. 18

19 elements of elements elements elements of of of elements of Group Group IIA have Group a Group VA Group have VIA have VIIA a have a a IA have a +1 charge +2 charge -3 charge -2 charge -1 charge 19

20 Writing Formulas From Names of Compounds 20

21 A chemical compound must have a net charge of zero. 21

22 If the compound contains ions, then the charges on all of the ions must add to zero. 22

23 Write the formula of calcium chloride. Step 1. Write down the formulas of the ions. Ca 2+ Cl - Step 2. Combine the smallest numbers of Ca 2+ and Cl - so that the sum of the charges The cation The is anion is written equals written first. zero. second. (Ca 2+ ) + 2(Cl - ) = 0 (2+) + 2(1-) = 0 The correct formula is CaCl 2 The lowest common multiple of +2 and 123 is 2

24 Write the formula of barium phosphide. Step 1. Write down the formulas of the ions. Ba 2+ P 3- Step 2. Combine the smallest numbers of Ba 2+ and P 3- so that the sum of the charges The cation The anion is is written written equals first. second. zero. 3(Ba 2+ ) + 2(P 3- ) = 0 3(2+) + 2(3-) = 0 The correct formula is Ba 3 P 2 The lowest common multiple of +2 and 324 is 6

25 Binary Compounds 25

26 Binary compounds contain two different elements only. 26

27 Naming Binary Compounds 27

28 Binary ionic compounds consist of a metal combined with a non-metal. 28

29 Binary Ionic Compounds Containing a Metal Forming Only One Type of Cation 29

30 The chemical name is composed of the name of the metal followed by the name of the nonmetal which has been modified to an identifying stem plus the suffix ide. The number of atoms of each element present is not expressed in the name. 30

31 Name of Metal + Stem of Nonmetal with -ide ending 31

32 Examples 32

33 Compound NaCl name of metal Name sodium chloride nonmetal stem 33

34 Compound MgCl 2 name of metal Name magnesium chloride nonmetal stem 34

35 Binary Ionic Compounds Containing a Metal That Can Form Two or More Types of Cations 35

36 The Stock System 36

37 In IUPAC the Stock devised System the the Stock charge System on the of cation is designated nomenclature byto a name Roman compounds numeral placed of in parentheses metals that immediately have more than following one type theof name of the cation. metal. Cation Charge Roman Numeral I II III IV V The stem of the nonmetal name ends in -ide. 37

38 Lower Charge Stock System Higher Charge Element Formula Name Formula Name Copper Cu + copper (I) Cu 2+ copper (II) Iron Fe 2+ iron(ii) Fe 3+ iron(iii) Lead Pb 2+ lead (II) Pb 4+ lead(iv) Mercury Hg 2 2+ mercury(i) Hg 2+ mercury(ii) Tin Sn 2+ Tin(II) Sn 4+ Tin (IV) 38

39 Examples 39

40 iron(ii) chloride FeCl 2 compound ion charge name name +2-1 iron(ii) chloride iron(iii) chloride FeCl 3 +3 iron(iii) -1 chloride 40

41 Binary Compounds Containing Two Nonmetals 41

42 Compounds between nonmetals are molecular, not ionic. 42

43 In a compound formed between two nonmetals, the element that appears first in the formula is named first. 43

44 Prefixes 44

45 Prefixes are used in a name to denote the number of atoms of each element present in a formula unit. Mono is rarely used when naming the first element, but mono is used in naming the second element (e.g. CO is carbon monoxide). mono = 1 di = 2 tri = 3 tetra = 4 penta = 5 hexa = 6 hepta = 7 octa = 8 nona = 9 deca = 10 45

46 Examples 46

47 dinitrogen trioxide N 2 O 3 indicates two nitrogen atoms indicates three oxygen atoms 47

48 dichlorine heptaoxide Cl 2 O 7 indicates two chlorine atoms indicates seven oxygen atoms Why does chlorine appear first in the formula and oxygen second? Oxygen is more electronegative than chlorine; the more electronegative element appears second in the formula and the name. Electronegativity is the relative ability of an atom in a bond to attract the bonding electrons toward itself and away from the 48 atom it is bonded to.

49 Electronegativity increases from the lower left to the upper right for representative elements. 49

50 Step by Step Approach to Naming a Binary Molecular Compounds, PCl 5 Step 1 Phosphorous and chlorine are nonmetals so the rules for naming a binary molecular compound applies. Phosphorous is named first and chlorine second. (recall Cl is more electronegative: See 11.6). Therefore, in the name, phosphorous remains phosphorous and chlorine becomes chloride. 50

51 Step by Step Approach to Naming Binary Molecular Compounds, Cont. Step 2 No prefix is needed for phosphorous because there is only one phosphorous atom. The prefix penta- is used with chloride because there are 5 chlorine atoms present. Step 3 The name is phosphorous pentachloride. 51

52 Examples 52

53 Cl 2 O 3 dichlorine trioxide 53

54 N 2 O 3 dinitrogen trioxide 54

55 Acids Derived from Binary Compounds of Hydrogen 55

56 Certain binary hydrogen compounds, when dissolved in water, form solutions that have acid properties. The aqueous solutions of these compounds are given acid names. 56

57 Pure solid or gaseous compound HCl Hydrogen Chloride Dissolved in water HCl Hydrochloric acid 57

58 To write the formula of binary acids write the symbol of hydrogen first. After hydrogen, write the symbol of the second element; typically a nonmetal. To name binary acids, place the prefix hydro- in front of the stem of the nonmetal name. Then place the suffix -ic after the stem of the nonmetal name followed by acid. 58

59 Examples 59

60 Pure Solid or Gaseous Compound HCl hydrogen chloride 60

61 Dissolved in Water HCl hydrochloric acid 61

62 Pure Solis or Gaseous Compound HI hydrogen iodide 62

63 Dissolved in Water HI hydroiodic acid 63

64 Naming Compounds Containing Polyatomic Ions 64

65 A polyatomic ion is an ion that contains two or more elements. The nitrate anion is an example. NO

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67 When naming a compound containing a polyatomic ion, name the cation first and then name the anion. Na CO 2 3 In writing the formula, the cation(s) appears first followed by the polyatomic ion. 67

68 Oxy-acids 68

69 Oxy-acids contain hydrogen, a nonmetal, or a metal, and oxygen. HClO 3 or H 2 CrO 4 69

70 Hydrogen in an oxy-acid is not expressed in the acid name. The word acid in the name indicates the presence of hydrogen. 70

71 Naming Oxy-Acids of Chlorine HClO 4 HClO 3 HClO 2 HClO HCl Perchloric Acid Chloric Acid Chlorous Acid Hypochlorous Acid Hydrochloric Acid +1 oxygen Root Acid - 1 oxygen -2 oxygens No oxygen* * Please note HCl is not an oxy-acid

72 Prefixes and Suffixes of Oxy-anions 72

73 Naming Oxy-Anions of Chlorine ClO - 4 ClO - 3 ClO - 2 ClO - Cl - Perchlorate Chlorate Chlorite Hypochlorite Chloride +1 oxygen Root Base - 1 oxygen -2 oxygens No oxygen* * Please note Cl - is not an oxy-anion

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