Classifying Matter Chapter5: Molecule & Compounds

5.2-5.5

Day One

Polyatomic Ions • Chlorate

• Carbonate

• Phosphate

• Ammonium

• Acetate

• Iodate

• Nitrate

• Cyanide

• Bicarbonate

• Sulfate

• Hydroxide

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Law of Constant Composition All pure substances have constant

composition.› All samples of a pure substance contain the same

elements in the same percentages (ratios).› Mixtures have variable composition.

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Compounds Display Constant CompositionIf we decompose water by electrolysis, we find 16.0 grams of oxygen to every 2.00 grams of hydrogen. Water has a constant mass ratio of oxygen to hydrogen of 8.0.

mass of oxygenMass Ratio mass of hydrogen

16.0 g 8.02.0 g

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Why Do Compounds ShowConstant Composition?

The smallest piece of a compound is called a molecule

Every molecule of a compound has the same number and type of atoms

All the molecules of a compound are identical, every sample will have the same ratio of the elements as well as the same properties

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Formulas Describe Compounds A compound is a distinct substance that is composed of

atoms of two or more elements

Describe the compound by describing the number and type of each atom in the simplest unit of the compound› Molecules or ions

Each element is represented by its letter symbol

The number of atoms of each element is written as a subscript› If there is only one atom, the 1 subscript is not written

Polyatomic groups are placed in parentheses › Polyatomic ions come as packages!!! › If more than one

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Practice—Determine the Total Number of Atoms or Ions in One Formula Unit of Each of the Following.

Mg(C2H3O2)2

(Hg2)3(PO4)2

1 Mg + 4 C + 6 H + 4 O = 15

6 Hg + 2 P + 8 O = 16

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Classifying Materials Atomic elements = Elements

whose particles are single atoms Molecular elements(diatomic) =

Elements whose particles are multi-atom molecules

Molecular compounds = Compounds whose particles are molecules made of only nonmetals.

Ionic compounds = Compounds whose particles are cations and anions.

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Molecular Elements Certain elements occur as diatomic

molecules. 7 diatomic elements—The Rule of 7s

› The seventh element is H2. H O N F Cl Br I

H2

Cl2

Br2

I2

7N2 O2 F2

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Molecular Compounds Two or more

nonmetals

Smallest unit is a molecule

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Ionic Compounds

Metals + nonmetals

No individual molecule units, instead have a 3-dimensional array of cations and anions made of formula units.

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Classify Each of the Following as Either an Atomic Element, Molecular Element, Molecular Compound, or Ionic Compound.

Aluminum, Al

Aluminum chloride, AlCl3

Chlorine, Cl2

Acetone, C3H6O

Carbon monoxide, CO

Cobalt, Co

Ionic vs. Covalent Com

pounds

IONICCOVALENT

Formed from two ions

Consists of a METAL and a nonmetal or polyatomic ion

Formed from two NONMETALS

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Ionic Compounds Ionic compounds are made of ions. Ionic compounds always contain cations

and anions› Cations = + charged ions; anions = − charged

ions. The sum of the + charges of the cations

must equal the sum of the − charges of the anions

The overall charge of a compound is ZERO!!

Writing Formulas for IONIC Compounds

1. Write the elemental symbol for each element

2. Write the charges for each element (How do I figure this out?)

3. Pull the switcheroo!

4. Reduce subscripts to smallest whole number ratio

Example Magnesium Fluoride

Ammonium Sulfide

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Practice—What Are the Formulas for Compounds Made from the Following Ions?

Potassium ion with a nitride ion.

Calcium ion with a bromide ion.

Aluminum ion with a sulfide ion.

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Practice—What Are the Formulas for Compounds Made from the Following Ions?

Potassium ion with a sulfate ion

Calcium ion with a hydroxide

Aluminum ion with an acetate ion.

Writing Formulas for Covalent (Molecular) Compounds

1. Write the elemental symbols for the two elements

2. Use the prefix to determine the subscripts for each element

Greek Prefixes

1- mono 2- di 3- tri4- tetra5- penta

6- hexa7- hepta8- octa9- nona 10- deca

Let’s Try a Few Carbon Dioxide

Dinitrogen pentaoxide

Diphosphorus trichloride

Assignment Problem Set #1

› Page 151 #23, 31, 33, 37, 39, 41, 49, 51, 53, 70

5.6-5.8

Day Two

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Major Classes Ionic compounds.

› Metal + nonmetal(s). Metal first in formula.

› Binary ionic or compounds with polyatomic ions.

Molecular compounds.› 2 or more nonmetals.› Binary molecular (or binary covalent).

2 nonmetals.› Acids—Formula starts with H.

Though acids are molecular, they behave as ionic when dissolved in water.

May be binary or oxyacid.

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Classifying Compounds Compounds containing a metal and a nonmetal

= Binary ionic› Type I and II

Compounds containing a polyatomic ion = Ionic with polyatomic ion

Compounds containing two nonmetals = Binary molecular compounds.

Compounds containing H and a nonmetal = Binary acids.

Compounds containing H and a polyatomic ion = Oxyacids.

Tro's "Introductory Chemistry", Chapter 5 27

Type I Binary Ionic Compounds Contain metal cation + nonmetal anion. Metal listed first in formula and name.1. Name metal cation first, name nonmetal

anion second.2. Cation name is the metal name.3. Nonmetal anion named by changing the

ending on the nonmetal name to –ide.

Lets try a few • KBr

• MgCl2

• CaO

• LiBr

Tro's "Introductory Chemistry", Chapter 5 29

Type II Binary Ionic Compounds Contain metal cation + nonmetal anion. Metal listed first in formula and name.1. Name metal cation first, name nonmetal

anion second2. Metal cation name is the metal name

followed by a roman numeral in parentheses to indicate its charge› Determine charge from anion charge

3. Nonmetal anion named by changing the ending on the nonmetal name to –ide.

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Practice─Name the Following Compounds.

TiCl4

PbBr2

Fe2S3

Naming Ionic Compounds (Ternary)

• Metal and a polyatomic ion

1. Name the metal

2. Name the polyatomic ion

** DO NOT CHANGE THE ENDING!!!!

Let’s Try a Few KNO3

Mg(OH)2

NH4NO3

Covalent (Molecular) Compounds

• Remember its formed from two nonmetals

1. Name the two elements

2. Add –ide to the end of the second element

3. Add prefixes to the elements that represent the number of atoms in the molecule

Lets Try a Few CCl4

BCl3

SF6

CO

Assignment Problem Set #2

› Page 151 #55,57,59, 61, 67, 68, 71

5.9

Day Three

Polyatomic Ions List II Bromate

Chromate

Dichromate

Permanganate

Thiosulfate

Naming Polyatomic Ions Didn’t you say we had to memorize

these?

Lets look at the polyatomic ions and how they differ!!!

40

Acids Acids are molecular compounds that

form H+ when dissolved in water

Sour taste Dissolve many metals

› Like Zn, Fe, Mg, but not Au, Ag, Pt.

Formula generally starts with H› E.g., HCl, H2SO4.

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Acids, Continued Contain H+1 cation

and anion› In aqueous solution

Binary acids have H+1 and nonmetal

Oxyacids have H+1 and polyatomic

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Naming Binary Acids Write a hydro- prefix. Follow with the nonmetal name. Change ending on nonmetal name to –

ic. Write the word acid at the end of the

name.

Let’s try a Few HBr

HF

HI

Naming Oxyacids

•Perbromic Acid HBrO4

•Bromic Acid HBrO3

•Bromous AcidHBrO2

•Hypobromous AcidHBrO

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Practice─Name the Following

1. H2S

2. HClO3

3. HNO2

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Writing Formulas for Acids When name ends in acid, formulas starts

with H.

Hydro- prefix means it is binary acid, no prefix means it is an oxyacid.

For an oxyacid, if ending is –ic, polyatomic ion ends in –ate; if ending is –ous, polyatomic ion ends in –ous.

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Practice—What Are the Formulas for the Following Acids?

1. Chloric acid

2. Phosphoric acid

3. Hydrobromic acid

Assignment Problem Set #3

› Page 151 # 73, 74, 75, 76

5.11

Day Five

Tro's "Introductory Chemistry", Chapter 5 50

Lets Try a Few!! Potassium Chloride

Aluminum Oxide

Potassium Sulfide

Magnesium Hydroxide

Lets Try A few HNO3

H2SO4

H2SO3

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Formula Mass The mass of an individual molecule or

formula unit Also known as molecular mass or

molecular weight Sum of the masses of the atoms in a

single molecule or formula unit› Whole = Sum of the parts.

Mass of 1 molecule of H2O = 2(1.01 amu H) + 16.00 amu O =

18.02 amu.

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Practice—Calculate the Formula Mass of Al2(SO4)3.

Assignment Review Sheet

Ionic vs. Covalent Lab

Day Six