Presentation on theme: "Unit 7: Changes in Matter"— Presentation transcript:
1 Unit 7: Changes in Matter Ch. 19 – Molecules and Compounds
2 19.1 Bonding and Molecules19.2 Chemical Formulas19.3 Comparing Molecules
3 Chapter 19 Learning Goals Relate the chemical behavior of an element, including bonding, to its placement on the periodic table.Identify how elements form chemical bonds and the role of electrons in bonding.Predict the chemical formulas of compounds made up of two different elements.Write chemical formulas for compounds made up of many different types of elements.Calculate the formula mass of a compound and compare different compounds based on their formula masses.Identify the environmental and economic impact of recycling plastics.
5 I. CompoundsA. Compounds1. chemical bondsa. the attractive force that holds atoms or ions together
6 2. A compound always has the same chemical formula a. water – H2Ob. salt – NaClc. table sugar – C12H22O11
7 3. Molecular formulaa. a chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of atomsb. H2Oc. NaCld. C12H22O11
8 4. Chemical Structure/Structural Formula a. a formula that indicates the location of atoms, groups, or ions relative to one another in a moleculeb. indicates the number and location of chemical bonds
10 B. How does structure affect properties? 1. compounds with network structures are strong solidsa. quartz and sand – SiO2b. high melting and boiling pointsc. requires a lot of energy to break the bonds
11 2. Some networks are made of bonded positive and negative ions a. salt – NaClb. Na+ and Cl- ions are bonded together forming large networksc. increases strength, high melting and boiling points
12 3. Some compounds are made of molecules a. table sugar – C12H22O11b. strong attraction between the atoms, but weak attraction between the molecules
13 19.1 Bonding and Molecules Key Question: Why do atoms form chemical bonds?
14 II. Ionic and Covalent Bonding A. What holds bonded atoms together?1. the outermost energy level of a bonded atom is full of electronsa. valence electrons – atoms want 82. bonds can bend and stretch without breaking
28 3. ie – water (H2O) and sugar (C12H22O11) 4. usually have a low melting point5. do not conduct electricity because they are not charged6. atoms are not always shared equally
29 D. Polyatomic Ions1. an ion made of two or more atomsa. hydroxide ion - OH-b. carbonate ion – CO32-c. ammonium ion - NH4+2. some compounds have both ionic and covalent bonds – made of polyatomic ions
30 III. Compound Names and Formulas A. Naming Ionic Compounds1. Names of cations include the elements of which they are composed2. Names of anions are altered names of elements3. Some elements must show their charge
31 4. Writing Chemical Formulas *What is the chemical formula for aluminum fluoride?a. list the symbols for each ionaluminumfluorideb. write the symbols for the ions with the cation first
32 c. Find the least common multiple of the ions’ charges - least common multiple of _____ and ______ is ______- to get _____ positive charged, need only ______- to get _____ negative charges, need _______
33 d. Write the chemical formula indicating with subscripts how many of each ion are needed to make a neutral compound
34 5. Determining the charge of a transition metal cation Iron (III) ion and Oxide ionFe chargeOxide charge
35 c. titanium (III) nitride d. cobalt (III) hydroxide 6. Problemsa. lithium oxideb. beryllium chloridec. titanium (III) nitrided. cobalt (III) hydroxidee. magnesium bromidef. rubidium oxideg. lithium nitrideh. potassium sulfateA – Li2O; b – BeCl2; c – TiN; d – Co(OH)3; e – MgBr2; f – Rb2O; g – Li3N; h – K2SO4
36 B. Naming Covalent Compounds 1. numerical prefixes are used to name covalent compounds of two elements2. mono is not used on the first element in the formula
37 3. Problems a. N2O4 b. BF3 c. CO d. CO2 A – dinitrogen tetraoxide; b – boron triflurodie; c – carbon monoxide; d – carbon dioxide
38 IV. Organic and Biochemical Compounds A. Organic compounds1. covalently bonded compound that contains carbon2. organism – a living thing3. organisms are made of organic compounds
39 B. Examples of Organic Compounds 1. carbohydrates2. proteins3. lipids (ie – fats)4. nucleic acids (ie – DNA)
40 19.2 Chemical Formulas Key Question: Why do atoms combine in certain ratios?*Read text section 19.2 AFTER Investigation 19.2
41 19.2 Chemical FormulasAll compounds have an electrical charge of zero; that is, they are neutral.
42 19.2 Oxidation NumberAn oxidation number indicates how many electrons are lost, gained, or shared when bonding occurs.
51 19.3 Comparing CompoundsThe Avogadro number is the number of atoms in the atomic mass of an element or the number of molecules in the formula mass of a compound when these masses are expressed in grams.One set of 6.02 x 1023 atoms or molecules is also referred to as a mole of that substance.