COMPOUNDS FORM ACCORDING

Transcription

1 COMPOUNDS FORM ACCORDING TO A SET OF RULES. Unit B: Matter and Chemical Change Section NAMING COMPOUNDS Every compound has a chemical name and a chemical formula: from the shampoo in your bathroom to the gasoline in your garage. 2 1

2 LEARNING OUTCOMES Key Concepts periodic table elements, compounds, and atomic theory chemical nomenclature Learning Outcomes distinguish between ionic and molecular compounds, and describe the properties of some common examples of each read and interpret chemical formulas for compounds of two elements, and give the IUPAC name and common name of these compounds identify/describe chemicals commonly found in the home, and write the chemical symbols identify examples of combining ratios/number of atoms per molecule found in some common materials, and use information on ion charges to predict combining ratios in ionic compounds of two elements assemble or draw simple models of molecular and ionic compounds^ 3 *CHEMICAL FORMULA* Combination of symbols that represent a compound The formula identifies: the elements in the compound, and the amount of each element Example: The chemical formula for salt is NaCl 4 2

3 EXAMPLE: ETHANOL C 2 H 5 OH 5 NAMING CHEMICAL COMPOUNDS Until the 18th century, no standardized system existed for naming chemicals. This created confusion because the names for chemical compounds varied from country to country and scientist to scientist. Example: hydrochloric acid and muriatic acid refer to the same thing. 6 3

4 NAMING CHEMICAL COMPOUNDS (CONTINUED) In 1787, a French chemist named Guyton de Morveau created a naming system, or nomenclature, for compounds. He decided to use the chemical name for each element in the compound, always putting the metal element first. 7 IUPAC Since 1920, the International Union of Pure and Applied Chemistry (IUPAC) has been responsible for determining the appropriate name for each compound. They are also looked to when there are discrepancies in spelling. Example: Aluminium vs Aluminum Sulphur vs Sulfur 8 4

5 CHEMICAL NAMES AND FORMULAS If you know the formula for a compound, you will be able to determine its chemical name. If you know the name of a compound, you will be able to determine its formula. Chemical name Chemical formula 9 -IDE SUFFIX You will notice that some compounds have a chemical name where the name ends in -ide We ll learn later when to write names using -ide. For now, just look at the first part of the second word to help you figure out which element it represents. Example: sodium chloride 10 5

6 INTERPRETING CHEMICAL NAMES AND FORMULAS What is the chemical formula for water? H 2 O Notice that next to the H is a small 2 as a subscript. ( Sub means below.) The 2 indicates that there are two atoms of hydrogen to go with every atom of oxygen in water. 11 INTERPRETING CHEMICAL NAMES AND FORMULAS (CONTINUED) No subscript number indicates that only one atom of that element is needed

7 EXAMPLE: WATER Fill in the following chart for water. Compound Water Chemical Formula Elements # of Atoms of Each Total # of Atoms 13 EXAMPLE: TABLE SALT Fill in the following chart for table salt. Compound (Chemical name) Chemical Formula Elements # of Atoms of Each Total # of Atoms 14 7

8 MODELS OF ATOMS Table salt s chemical name, sodium chloride, is a compound made of one atom of sodium and one atom of chlorine 15 MODELS OF ATOMS (CONTINUED) What would the model for water look like? 16 8

9 PHYSICAL STATE OF A COMPOUND Indicating the state of the chemical at room temperature is another common notation. Recall: solid (s) Ex: NaCl (s) liquid (l ) H 2 O (l) gas (g) O 2(g) 17 AQUEOUS SOLUTIONS Recall that aqueous solutions are substances dissolved in water. A subscript aq in parentheses is added to the formula (aqueous comes from the Greek word aqua which means water). Example: sodium chloride dissolved in water would be written as NaCl (aq). 18 9

10 - SKILL PRACTICE PG C & R PG. 143 # 3, 4 Assignment 19 SKILL PRACTICE; PG. 142 Compound Elements in Compound # of Atoms in Each Element Drawing of Compound 20 10

11 C & R PG. 143 # 3, 4 21 C & R PG. 143 # 3,

12 C&R #4D - CHEMICAL NAME & PHYSICAL STATE : GLUCOSE - SOLID Chemical Formula : C 6 H 12 O 6 (s) The chemical formula for glucose tells us that each molecule is made of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms. Atomic model 23 TOPIC 3.2: IONIC COMPOUNDS Textbook: pg

13 LEARNING OUTCOMES Key Concepts periodic table elements, compounds, and atomic theory chemical nomenclature Learning Outcomes distinguish between ionic and molecular compounds, and describe the properties of some common examples of each read and interpret chemical formulas for compounds of two elements, and give the IUPAC name and common name of these compounds identify/describe chemicals commonly found in the home, and write the chemical symbols identify examples of combining ratios/number of atoms per molecule found in some common materials, and use information on ion charges to predict combining ratios in ionic compounds of two elements assemble or draw simple models of molecular and ionic compounds 25 *IONIC COMPOUND* pure substances formed as a result of the attraction between particles of opposite charges, called ions Ionic compound = metal + non-metal + Ionic compound 26 13

14 *IONS* An ion is an atom that has become electrically charged because it has lost or gained electrons; a positive ion is an atom that has lost one or more electrons; a negative ion is an atom that has gained one or more electrons e- e- e- e- ^When an ionic compound is dissolved in water, the metal and non-metal form an aqueous solution of ions.^ 27 ION CHARGES 28 14

15 IONIC COMPOUND Ionic Ions + - Charges 29 POLYATOMIC IONS A group of atoms acting as one ^ Poly means many. ^ Example: carbonate ion (limestone): CO 2-3 sulfate ion: SO

16 EXCEPTION! If the non-metal ion (-) is a polyatomic ion, the name remains unchanged. Example: CaCO 3 Ca 2+ and CO PROPERTIES OF IONIC COMPOUNDS Attraction between particles of opposite charges (ions) High melting points Good electrical conductors (when melted or dissolved) Distinct crystal shape Solids at room temperature Example: Table Salt melts at 801 C

17 ^ALL IONIC COMPOUNDS MODEL DIFFERENT CRYSTAL SHAPES.^ ^Naturally occurring elements are made of atoms of different sizes and properties that combine in many ways to form crystals. The huge range of temperatures and pressures within the Earth contributes to this diversity.^ 33 CRYSTAL When ions combine, they form a crystal

18 ION CHARGES An ionic charge is written as a superscript and is (+) or ( ) with a number to indicate how many electrons were added or taken away. Textbook pg

19 ^RECALL: IONIC COMPOUNDS metal + non-metal Positively charged ions + negatively-charged ions^ EX: SODIUM CHLORIDE IS AN IONIC COMPOUND. Chemical formula: Common name: Chemical name: NaCl table salt sodium chloride ^When the compound is dissolved in water, the metal and non-metal form an aqueous solution of ions.^ 38 19

20 NAMING IONIC COMPOUNDS Example: NaCl (s) 1. Write the chemical name of the metal (+) ion first. NaCl (s) metal = Na = sodium 2. Write the chemical name of the non-metal (-) ion, but change its ending to -ide. NaCl (s) non-metal = Cl = chlorine We write chloride instead of chlorine Our answer: NaCl (s) = sodium chloride 39 ALWAYS AN EXCEPTION... There is one exception to these naming rules. Where negative ions are polyatomic ions, the name remains unchanged. Example: Limestone s chemical name remains calcium carbonate

21 Some elements with more than one ion charge use a roman numeral written in brackets in its chemical name to clearly show which ion is being used. Copper(II) Sulfate Copper(I) Sulfate 41 NAMING COMPOUNDS 42 21

22 USING ION CHARGES & CHEMICAL NAMES TO WRITE FORMULAS: Step 1: Print the metal element s name, symbol and ion charge, and the non-metal s name, symbol and ion charge. Example: Calcium chloride Metal: Calcium Ca 2+ Non-metal: Chlorine Cl 1-43 Step 2: Balance the ion charges (^the positive ion must balance with the negative ion^) We have: Ca 2+ = Cl 1- We Need: Ca 2+ = Cl 1- + Cl

23 Step 3: Write the formula by indicating how many atoms of each element are in it. CaCl 2 45 ^ANOTHER WAY TO BALANCE THE IONS^ In step 2, you can also balance the ions using the following method: 1. Write the ions with their charges. 2. Write the charge as a subscript at the opposite ion, without the (+) or (-) sign. 3. If an ion has a subscript of 1, you don t have to write it down. Simplify the ratio, if possible. Example: calcium chloride Ca 2+ Cl 1- Ca Cl

24 YOUR TURN! Write the chemical formula for aluminum oxide. 47 ^OXYANIONS (polyatomic anions containing oxygen) are named with ite or ate, for a lesser or greater quantity of oxygen.^ Nitrite NO 2 - Nitrate NO

25 ^OTHER POLYATOMIC IONS:^ ^Nitrate NO 3 1-^ ^Nitrite NO 2 1-^ ^Carbonate CO 3 2- ^ ^Sulfate SO 4 2- ^ ^Hydroxide OH 1- ^ ^Cyanide CN 1- ^ ^Ammonium NH 4 1+ ^ 49 ^POLY-ATOMIC (MANY ATOMS) IONS^ ^Ex: Nitrite NO 2 is a polyatomic ion.^ Let s see what the chemical formula is for Calcium Nitrite. (pesticide) 2+ = Ca 1- = NO 2 Together it forms Ca(NO 2 )

26 TRY TO MAKE CALCIUM CARBONATE IF CO 3 2- is carbonate. Calcium carbonate is also known as limestone. = Ca CO 3 51 ^LOOKING BACK ^ ^How many of each element was there?^ Al 2 O 3 NaCl Ca(NO 2 ) 2 H 2 O NO

27 ASSIGNMENT C&R page 149 #7-8 Chemical formula for the compound Elements in each compound Number of atoms in each element Name of metal (+) ion and the charge Name of nonmetal (-) ion with ide and the charge Name of compound sodium fluoride LiCl (s) TOPIC 3.3: MOLECULAR COMPOUNDS Textbook pg

28 LEARNING OUTCOMES Key Concepts periodic table elements, compounds, and atomic theory chemical nomenclature Learning Outcomes distinguish between ionic and molecular compounds, and describe the properties of some common examples of each read and interpret chemical formulas for compounds of two elements, and give the IUPAC name and common name of these compounds identify/describe chemicals commonly found in the home, and write the chemical symbols identify examples of combining ratios/number of atoms per molecule found in some common materials, and use information on ion charges to predict combining ratios in ionic compounds of two elements assemble or draw simple models of molecular and ionic compounds 55 MOLECULAR COMPOUNDS When non-metals combine, a pure substance called a molecule or a molecular compound is formed. You can think of atoms that have bonded together

29 LOOKING BACK Which chemicals are IONIC, and which are MOLECULAR? Al 2 O 3 NaCl Ca(NO 2 ) 2 H 2 O NO 2 57 PROPERTIES OF MOLECULAR COMPOUNDS They can be solids, liquids, or gases at room temperature. They tend to be good insulators, or poor conductors of electricity. They also have relatively low melting and boiling points because the forces between the molecules are weak. Examples: sugar, acetylene, and water

30 ^MOLECULAR COMPOUNDS INCLUDE:^ ^DNA^ e e e 59 e EXAMPLES: Sugar (sucrose) sweetener, preservative C 12 H 22 O 11 Glucose - energy source for living things C 6 H 12 O 6 Acetylene (ethyne) making chemicals C 2 H

31 ^SUGAR CRYSTAL^ ^The top picture looks like salt crystals, but if you take a closer look, you will see that SUGAR crystals are HEXAGONAL.^

32 WRITING FORMULAS FOR MOLECULAR COMPOUNDS *The ion charge is not used in the formulas of molecular compounds.* ^Writing formulas for molecular compounds is similar to writing formulas for ionic compounds, except that no ions are present and the ion charge is not used in the formulas. This makes it hard to predict how non-metals combine. The chemical formula still tells us how many of each type of atom is present in the molecule. 63 EXAMPLES OF MOLECULAR COMPOUNDS 64 32

33 NAMING OF MOLECULAR COMPOUNDS All molecular compounds can be named using the following rules, except those containing hydrogen. Common names are used for molecular compounds containing hydrogen. 65 PREFIX RULES Recall: suffix adds on to the end prefix adds on the front 66 33

34 NAMING OF MOLECULAR COMPOUNDS (CONTINUED) Example: N 2 O 1. The first element in N 2 O N = the compound uses the element name just like ionic compounds. 2. The second element in the compound has the suffix ide just like ionic compounds. 3. A prefix is used to specify the number of atoms of each element in the compound. 4. An exception to rule 3 is when the first element has only one atom, the prefix mono is not used. 67 NAMING OF MOLECULAR COMPOUNDS (CONTINUED) 1. The first element in the compound uses the element name just like ionic compounds. 2. The second element in the compound has the suffix ide just like ionic compounds. 3. A prefix is used to specify the number of atoms of each element in the compound. 4. An exception to rule 3 is when the first element has only one atom, the prefix mono is not used. Example: CO 2 is read as carbon dioxide, not monocarbon dioxide. Example: N 2 O N 2 O N = nitrogen N 2 O O = oxygen Oxygen oxide 68 34

35 NAMING OF MOLECULAR COMPOUNDS (CONTINUED) 1. The first element in the compound uses the element name just like ionic compounds. 2. The second element in the compound has the suffix ide just like ionic compounds. 3. A prefix is used to specify the number of atoms of each element in the compound. 4. An exception to rule 3 is when the first element has only one atom, the prefix mono is not used. Example: N 2 O N 2 O N = nitrogen N 2 O O = oxygen Oxygen oxide 2 N s di dinitrogen 1 O mono Monoxide N 2 O has a chemical name of dinitrogen monoxide. 69 NAMING OF MOLECULAR COMPOUNDS (CONTINUED) 1. The first element in the compound uses the element name just like ionic compounds. 2. The second element in the compound has the suffix ide just like ionic compounds. 3. A prefix is used to specify the number of atoms of each element in the compound. 4. An exception to rule 3 is when the first element has only one atom, the prefix mono is not used. Example: CO Monocarbon monoxide CO has a chemical name of carbon monoxide

36 NAMING OF MOLECULAR COMPOUNDS (CONTINUED) 71 IONIC VS. MOLECULAR COMPOUNDS Ionic Compounds Molecular Compounds Relatively high melting and boiling points Solids at room temperature Good conductors of electricity Distinct crystal shape Examples: Relatively low melting and boiling points Solids, liquids, or gases at room temperature Poor conductors of electricity (they make good insulators) Examples: 72 36

37 HOMEWORK Check and Reflect pg. 153 #