Ch2.0 Lesson.notebook. February 08, Bell Activity. How do you think chemicals get their name? Who gives them their name?

Transcription

1 Bell Activity How do you think chemicals get their name? Who gives them their name? 1

2 Introduction to Naming 2

3 IUPAC system ensures that each pure substance has a single unique name. This is called its systematic name. IUPAC is the abbreviation for the International Union of Pure & Applied Chemistry. IUPAC names and formulas are important for communicating with people around the world so they know what chemical you are talking about. 3

4 Common names are not the same in every country but systematic names normally are. Examples: Common Name: salt Chemical Formula: sodium chloride Common Name: saltpetre Chemical Formula: potassium nitrate 4

5 Binary Molecular Compound Naming Rules Binary molecular compounds contain 2 non-metallic elements. Step 1: Start with the first element in the formula. This will be the first element in the name. Example: carbon is first in CO (g) Step 2: The -ide suffix is attached to the name of the second element Step 3: Prefixes are used to indicate how many atoms are present in one molecule. If the first element has only 1 atom, you do not write mono. 5

6 Molecular Compound Prefixes Prefix # of atoms mono 1 di 2 tri 3 tetra 4 penta 5 hexa 6 hepta 7 octa 8 nona 9 deca 10 6

7 Ionic Naming and Formulas Naming is easy!! First element is metal, just call it by element name. For second non-metallic element, add an ide. Ex. MgF 2(s) is magnesium fluoride. Chemical Formula: Step 1: Write out the symbols for both elements, metal before nonmetal. Step 2: Find the most common charge for both elements from your periodic table (Ex. Ca is 2+) Step 3: Find the lowest possible ratio where the total charge balances. (positive charge - negative charge= 0) 7

8 You must find the ratio of the chemical formula using the charge of the ions. Example: scandium oxide Sc 3+ O 2- The lowest common multiple is 6! So in order to get 6+ we need 2 Sc. To get 6- we need 3 O = 0 Sc 2 O 3(s) 8

9 Bell Activity Name the following chemicals using either the naming system for ionic or molecular compounds. 1) SF 3 2) Ca 3 N 2 3) Mg 3 P 2 4) NI 3 5) ZnF 2 9

10 (Ionic Notes) Cation Stock System Some cations can have more than one stable electron configuration. These metals are commonly transition metals. You can find the possible charges for these cations on the periodic table. The most common charge is listed first. 10

11 Cation Stock System 11

12 For example, copper can form Cu + or Cu 2+. Now here is the tricky part. How do you know which one? Example: Which copper ion is used in CuCl 2? There are two easy ways to figure this out. 12

13 Method 1 Reverse the 'criss-cross' rule. Be careful though, some formulas have reduced ratios Cu 1 Cl 2 Cu 2+ Cl 1- Method 2 Use both charges to figure out the chemical formula and match it. I think this way is easier dealing with reduced ratios. Cu 2+ Cl 1- Cu 1+ Cl 1- CuCl 2 CuCl 13

14 Dealing with Reduced Ratios: What manganese ion is used in MnO 2? Method 1 Reverse the 'criss-cross' rule. Mn 1 O 2 Mn 2+ O 1- But look, you cannot have O 1- because an oxygen ion is O 2-. This is your hint that the ratio has been reduced in this formula. Since the charge on an oxygen ion is double, you need to double that on manganese. Therefore, the charge on manganese is

15 Method 2 Use both charges to figure out the chemical formula. Mn 2+ O 2- Mn 4+ O 2- Mn 2 O 2 MnO Mn 2 O 4 MnO 2 Therefore, the charge must be 4+ 15

16 In order to show which ion it is (as they have different chemical properties) you must write it in the systematic name. This is done by placing the Roman Numeral corresponding to the charge of the cation in brackets after the cation name. Roman Numerals = I 6= VI 2= II 7= VII 3= III 8= VIII 4= IV 9= IX 5= V 10= X 16

17 Examples: iron(ii) oxide = FeO iron(iii) oxide= Fe 2 O 3 DO NOT WRITE IT IN THE FORMULA!! i.e. iron (III) oxide is not Fe 3 O The ionic formula can be used to find the charge on the cation so writing it in the formula is not necessary. 17

18 Bell Activity What would the formulae be for the following reactions? 1. Magnesium + Oxygen 2. Beryllium + Sulphur 3. Calcium + Nitrogen 4. Niobium (V) + Iodine 5. Sodium + Phosphorus 18

19 Polyatomic Ions A list of polyatomic ions can be found on your periodic table 19

20 Polyatomic ions are made of more then one element that are bonded together covalently. These elements end up having an overall charge so they are attracted to oppositely charged ions forming an ionic compound. Example: This molecule has a negative 1 charge because there are 9 protons but 10 electrons. charge = #protons - #electrons charge = 9-10 charge = -1 This is called the hydroxide ion. 20

21 Names for polyatomic ions are at the top of the periodic table. If you have more than 1 of a polyatomic ion, you must write this ion in brackets in the chemical formula. Ex. Ca(NO 3 ) 2 21

22 Examples - use the criss-cross rule (also remember ionic compounds are solid at room temperature and pressure) 1. What is the formula for ammonium fluoride? NH 1+ 4 F 1- NH 4 F (s) 2. What is the formula for sodium sulfate? Na 1+ SO 4 2- Na 2 SO 4(s) 3. What is the formula for calcium nitrate? Ca 2+ NO 3 1- Ca(NO 3 ) 2(s) Notice the brackets on NO 3. You need TWO NO 3 1- ions to provide 2 electrons (1 from each) to the Ca 2+, which requires 2 electrons. 4. What is the formula for iron(iii) sulfite? Fe SO 3 Fe 2 (SO 3 ) 3(s) 5. What is the name of NiCO 3? nickel(ii) carbonate 22

23 True or False? This guy has way too much free time. 23

24 Bell Activity What would be the formulae for the following chemicals? 1. Magnesium sulphate 2. Iron (III) nitrate 3. Tin (IV) chlorate 4. Aluminum hydroxide 24

25 Acids & Bases 25

26 Acids Sour tasting substance Turns blue litmus paper red Bases Slippery, bitter-tasting substance Turns red litmus paper blue ***Remember, if it RED it s an ACID (it rhymes)*** 26

27 Acids and bases have distinct properties that make them very useful. 27

28 Properties of Acids & Bases ACIDS BASES sour taste reacts with metals bitter taste slippery ph less than 7 ph greater than 7 conducts electricity corrosive conducts electricity corrosive 28

29 The ph scale is used to measure the strengths of acids and bases: With each step down in ph, the substance is 10 times more acidic. Acids and bases can be identified using indicators. Litmus paper is the most common indicator as it is produced from lichens and is inexpensive. 29

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31 Bell Activity List 3 different properties of acids & bases. Which is more dangerous- an acid or a base? 31

32 Naming Acids Cl H H O O O O H 32

33 What makes a substance an acid? Arrhenius proposed a theory that an acid is a substance that reacts and releases H + (aq) ions with water. For example when added to water HCl (g) H + (aq) + Cl - (aq) The aq or aqueous state means that the substance is in solution with water. All acids will have the (aq) state. However, if something has the (aq) state that does NOT necessarily mean it is an acid. 33

34 What makes a substance a base? A base releases OH - (aq) when in solution. For example, when added to water: NaOH (s) Na + (aq) + OH - (aq) Neutralization is the reaction of acid and base to produce water and salt. Example: NaOH (aq) + HCl (aq) H 2 O (l) + NaCl (aq) 34

35 Naming Acids If you see a chemical formula with hydrogen bonded to other non-metals in solution, this compound will have special naming rules. Acids Start With the Letter "H" (usually) Acids will have hydrogen listed first (except CH 3 COOH (aq) ). IUPAC convention for naming acids: they start with the word 'aqueous' followed by the ionic name. For example: HCl (aq) HNO 3(aq) H 2 SO 4(aq) is aqueous hydrogen chloride is aqueous hydrogen nitrate is aqueous hydrogen sulfate 35

36 Previous IUPAC convention (still very often used) Start with the ionic name... If the ionic name ends with "ide" hydro ic acid Remember: Hydro ride! Example: HCl (aq) is hydrochloric acid 36

37 If the ionic name ends with "ate" ic acid Remember: I ate something and it was ic. Example: H 2 SO 4(aq) is sulfuric acid 37

38 If the ionic name ends with "ite" ous acid Remember: "Fight us" Example: HNO 2(aq) is nitrous acid 38

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