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Unit 7: Changes in Matter

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1 Unit 7: Changes in Matter
Ch. 19 – Molecules and Compounds

2 19.1 Bonding and Molecules 19.2 Chemical Formulas 19.3 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.

4 Chapter 19 Vocabulary Terms
ionic bond polyatomic ion Product reactant Structural formula valence electron chemical bond chemical formula covalent bond energy level formula mass ion

5 I. Compounds A. Compounds 1. chemical bonds a. the attractive force that holds atoms or ions together

6 2. A compound always has the same chemical formula
a. water – H2O b. salt – NaCl c. table sugar – C12H22O11

7 3. Molecular formula a. a chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of atoms b. H2O c. NaCl d. 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 molecule b. indicates the number and location of chemical bonds


10 B. How does structure affect properties?
1. compounds with network structures are strong solids a. quartz and sand – SiO2 b. high melting and boiling points c. requires a lot of energy to break the bonds

11 2. Some networks are made of bonded positive and negative ions
a. salt – NaCl b. Na+ and Cl- ions are bonded together forming large networks c. increases strength, high melting and boiling points

12 3. Some compounds are made of molecules
a. table sugar – C12H22O11 b. 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 electrons a. valence electrons – atoms want 8 2. bonds can bend and stretch without breaking



17 19.1 The Octet Rule

18 19.1 Valence Electrons

19 B. Ionic Bonds 1. ionic bond a. a bond formed by the attraction between oppositely charged ions 2. ion a. an atom or group of atoms that has lost or gained one or more electrons

20 Ionic bonds are formed when atoms gain or lose electrons
Sodium and chlorine form an ionic bond to make sodium chloride (table salt)

21 b. Lithium atomic # atomic mass neutral ion # protons # neutrons # electrons CHARGE

22 c. Fluorine atomic # atomic mass neutral ion # protons # neutrons # electrons CHARGE

23 d. Anion 1) negatively charged ion e. Cation 1) positively charged ion

24 3. Formed by the transfer of electrons
a. ie – NaCl 4. Ionic compounds are in the form of networks, not molecules 5. When melted or dissolved in water, ionic compounds conduct electricity

25 6. Usually formed between metals and nonmetals

26 C. Covalent Bonds 1. a bond formed when atoms share one or more pairs of electrons

27 2. often formed between nonmetals

28 3. ie – water (H2O) and sugar (C12H22O11)
4. usually have a low melting point 5. do not conduct electricity because they are not charged 6. atoms are not always shared equally

29 D. Polyatomic Ions 1. an ion made of two or more atoms a. 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 Compounds 1. Names of cations include the elements of which they are composed 2. Names of anions are altered names of elements 3. 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 ion aluminum fluoride b. 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 ion Fe charge Oxide charge

35 c. titanium (III) nitride d. cobalt (III) hydroxide
6. Problems a. lithium oxide b. beryllium chloride c. titanium (III) nitride d. cobalt (III) hydroxide e. magnesium bromide f. rubidium oxide g. lithium nitride h. potassium sulfate A – 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 elements 2. 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 compounds 1. covalently bonded compound that contains carbon 2. organism – a living thing 3. organisms are made of organic compounds

39 B. Examples of Organic Compounds
1. carbohydrates 2. proteins 3. 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 Formulas All compounds have an electrical charge of zero; that is, they are neutral.

42 19.2 Oxidation Number An oxidation number indicates how many electrons are lost, gained, or shared when bonding occurs.


44 Common Polyatomic Ions


46 19.3 Comparing Molecules Key Question:
What is the meaning of a chemical formula? *Read text section 19.3 AFTER Investigation 19.3

47 19.3 Comparing Molecules One atom of hydrogen is 1/12 the mass of a carbon atom.

48 19.3 Comparing Molecules



51 19.3 Comparing Compounds The 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.

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