Nomenclature (Naming Compounds) and Chemical Formulas

Transcription

1 Nomenclature (Naming Compounds) and Chemical Formulas 1

2 Ions formed from a single atom Monatomic Ions Charges are determined by whether ion has lost electrons (+) or gained electrons (-) Symbols are written with the element symbol followed by a superscript that indicates the charge Mg +2 or N -3 Cations are named by the element name followed by ion Al = aluminum Al +3 = aluminum ion Anions are named with by dropping the ending of the element name and adding ide to it F = fluorine F - = fluoride N = nitrogen N -3 = nitride 2

3 Charges on some monatomic ions can be determined by location on periodic table. Group 1 +1 Group 2 +2 Group Group 14 don t form ions so no charge assigned Group 15-3 Group 16-2 Group 17-1 Group 18 don t form ions so no charge assigned 3

4 In your notes: 1. What would be the charge on a Lithium ion? 2. What would be the charge on a phosphorus ion? 3. Write the symbol for a Calcium ion. 4. Write the symbol for an Aluminum ion. 5. Write the symbol for Bromide ion. 6. Write the symbol for the Potassium ion. 7. Name O Name I - 9. Name Na Name N -3 4

5 To name binary ionic compounds (those containing only 2 elements) 1 st name the cation 2 nd name the anion ending with ide Example: Al 2 O 3 aluminum oxide 5

6 In your notes, name these 1. BaO 2. AgCl 3. KBr 4. MgO compounds 5. CaBr 2 6. MgCl 2 7. Na 2 S 8. SrF 2 9. KI 10. AlN 6

7 Writing Formulas for Binary Ionic Compounds For any ionic compound or covalent molecule, the total number of protons and electrons must be equal. So positive and negative charges must be equal. Compounds and molecules are NEUTRAL!!! Ex: Aluminum chloride 7

8 1 st - Write the symbol (including charge) for the cation and anion in the compound. Ex: strontium chloride strontium ion = Sr +2 chloride ion = Cl - 2 nd - Criss-cross the charges to the other ion and write them (without + & - signs) as subscripts. Ex: Sr 1 Cl 2 3 rd - If the subscript is a 1, or if both subscripts are the same number, do not write them. If subscripts can be reduced, do so. Ex: SrCl 2 Ba 2 O 2 BaO Pb 2 O 4 PbO 2 8

9 Write formulas for the binary ionic compounds formed between the following elements: 1. sodium and iodine 2. sodium and sulfur 3. potassium and sulfur 4. calcium and sulfur 9

10 Some elements can have more than one possible charge when forming ions. Ex: Cu 1+ and Cu 2+ The old system of naming ions used different endings to indicate which ion is referred to. -ous refers to ion with lower charge and -ic refers to ion with higher charge Ex: Cu 1+ = cuprous ion and Cu 2+ = cupric ion Fe 2+ = ferrous ion and Fe 3+ = ferric ion 10

11 The more common method is called the Stock System and uses roman numerals to identify this type of ion. Ex: Cu 1+ = Cu (I) called copper one or copper I Cu 2+ = Cu (II) called copper two or copper II Fe 2+ = Fe (II) called iron two or iron II Fe 3+ = Fe (III) called iron three or iron III To write formula, assign charge indicated by roman numeral and criss-cross as usual. copper I bromide iron III oxide 11

12 Write formulas and names for the binary ionic compounds formed between the following elements: 1. Potassium and iodine 2. Magnesium and fluorine 3. Sodium and sulfur 4. Aluminum and sulfur 5. Aluminum and nitrogen 6. Copper (II) and bromine 7. Iron (III) and oxygen 12

13 Do worksheet on Writing Binary Formulas and Naming Binary Compounds to turn in (worksheet pages 54 and 55) 13

14 Bellringer Name these compounds 1. KCl 2. CaI 2 3. Na 2 O 4. Al 2 O 3 5. MgS Write formulas for the compound formed between: 6. Lead II and oxygen 7. Iron III and sulfur 8. Tin II and iodine 14

15 Polyatomic Ions A group of covalently bonded atoms that have a charge Memorize formulas and names for these polyatomic ions (see text for others): ammonium hydroxide chlorate chlorite nitrate nitrite acetate carbonate Pay attention to element names and the suffixes -ate and -ite. chromate sulfate sulfite phosphate hydrogen carbonate 15

16 Naming Compounds with Polyatomic Example: Al(OH) 3 Ions Thought process: Contains metal so ionically bonded: name ions 3 different elements so not binary might not end in ide Must contain polyatomic ion figure out what part is polyatomic ion ( OH = hydroxide) Name metal and ion: aluminum hydroxide 16

17 Name These Compounds: Ca(OH) 2 KClO 3 NH 4 OH FeCrO 4 KClO 3 17

18 To write formulas using polyatomic ions: Charges must equal so compound is neutral Charges can be criss-crossed to make subscript If putting a subscript other than 1 after polyatomic ion, polyatomic ion MUST be inside parentheses Ex: (OH) 2 (PO 4 ) 2 The subscript then applies to all elements inside the parentheses 18

19 Complete Worksheet on Writing Formulas and Naming Compounds Containing Polyatomic Ions 19

20 Naming Binary Molecular Compounds Unlike ionic compounds, molecular compounds are composed of individual covalently bonded units, or molecules!!!!!! One nomenclature system for these covalently bonded molecules uses prefixes to tell number of atoms in molecule. Ex: CO 2 carbon dioxide 20

21 Number Prefix 1 mono- 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta- 8 octa- 9 nona- 10 deca- 21

22 Naming Binary Molecular Compounds Rules for prefix system: 1. Less-electronegative element is given first. It is given a prefix only if there is more than one atom. 2. Second element is named by combining (a) a prefix indicating the number of atoms, (b) the root of the second element, and (c) the ending ide. 3. The o or a at the end of a prefix is usually dropped when the word following the prefix begins with a vowel (example: monoxide or pentoxide). Unlike ionic formulas, molecular formulas are not reduced to the simplest ratio of atoms in the compound. The actual number of atoms is shown. Example: C 6 H 6 22

23 Name the following binary molecular compounds: a. SO 3 b. ICl 3 c. PBr 5 d. PF 5 e. XeF 4 f. CCl 4 23

24 Writing Formulas for Binary Molecules Use prefixes to determine subscripts NO CRISS-CROSS!!!!! Example: carbon dioxide CO 2 24

25 What would be formulas for the following compounds: a. Carbon tetraiodide b. Phosphorus trichloride c. Dinitrogen trioxide d. Carbon dioxide e. Dinitrogen pentoxide f. Sulfur hexafluoride 25

26 Complete the Worksheet on Naming Molecular Compounds (worksheet page 46) 26

27 Homework Complete the Homework Handout 27

28 Common Acids Acids are molecular compounds that might consist of two elements (binary) or hydrogen, oxygen, and a third element (oxyacids). Look on page 218 (black) or page 214 (blue) and copy the formulas and names of the common acids on the back of your Periodic Table. 28

29 Formula masses Formula mass = sum of the average mass units of all atoms represented in a formula Formula mass mostly used when referring to compounds. Formula mass units = amu 29

30 Find the formula mass for potassium chlorate. 1 st : What is the formula? 2 nd : How many atoms of each element do you have? 3 rd : Multiply the number of atoms of each element times its atomic mass units (amu from Periodic Table) 4 th : Find the sum of all amu. 30

31 Molar Mass Molar mass = mass of one (1) mole of a pure substance (element or molecule) For a compound/molecule, subscripts indicate the number of moles of each element Calculated the same as formula mass Molar mass units = g/mol Can be used as a conversion factor 31

32 Find the molar mass for iron III sulfite. 1 st : What is the formula? 2 nd : How many atoms of each element do you have? 3 rd : Multiply the number of atoms of each element times its molar mass (from Periodic Table) 4 th : Find the sum of all molar masses. 32

33 Complete the assigned Molar Mass Calculations. 33

34 Bellringer: Find the molar mass of each: a. Hydrogen sulfate b. Calcium nitrate c. Phosphate ion d. Magnesium chloride 34

35 Molar Mass can be used as a conversion factor to make calculations. What is the mass in grams of 2.50 mol of oxygen gas? (When pure, oxygen forms a diatomic molecule remember BrINClHOF?) Formula: Molar Mass: Calculate: 35

36 Determine the number of grams in each of the following quantities mol sodium chloride moles of CuSO 4. 5H 2 O 36

37 Determine the number of grams in each of the following quantities mol sodium chloride 150 g moles of CuSO 4. 5H 2 O 8.0 x 10 2 g ( g) 37

38 What is the mass in grams of 6.25 mol of copper (II) nitrate? Same information needed but solving for different unknown. 38

39 How many molecules are in g of aluminum chloride? 39

40 How many molecules are in g of aluminum chloride? AlCl 3 Molar mass = g 1 mol g x 1 mol x x molecules g 1 mol g AlCl 3 = x molecules 40

41 How many molecules are there in the following: a g H 2 SO 4 b. 125 g sugar, C 12 H 22 O 11 41

42 Complete the Molar Mass and Moles and Mass Worksheet (worksheet pages 49,50, and 51) 42

43 Percent Composition of an Egg 43

44 Percentage composition Find the percentage composition of Cu and S in copper (I) sulfide. Do your results equal 100%? 44

45 Bell Ringer In your notes Name and Find the % compositions of the following: a. PbCl 2 b.ba(no 3 ) 2 45

46 Section 7.4 Determining chemical formulas Empirical formula = formula showing the smallest whole-number mole ratio of atoms in the compound

47 Find the empirical formula of a compound that contains 32.38% Na, 22.65% S, and 44.99% O. 47

48 Analysis of a g sample of a compound known to contain only P and O indicates a P content of g. What is the empirical formula of this compound?

49 A compound is found to contain 36.48% Na, 25.41% S, and 38.11% O. Find its empirical formula.

50 Find the empirical formula of a compound that contains 53.70% Fe and 46.30% S.