9/26/11

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9/26/1164Counting Atoms with Coefficients

10/16/201363 Counting Atoms with Coefficient

10/16/2013

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Starter:How many atoms are in the following compounds:

H2O, NaCl, Cl2

ApplicationHow many atoms1. Ba3(PO4)2

2. 4Ba3(PO4)2

3. Al2(Cr2O7)3

4. 2Al2(Cr2O7)3

Connection: Counting Atoms with Coefficients Ws Exit: What is the difference between a carbon dioxide (CO2) and carbon monoxide (CO)?.

Practice:

Chemical Formula

# of elements

# of atoms

NaCl

CO2

C6H12

HgOH

Ag2S

Li2O

October 15, 2013AGENDA8.5 D.

I will be able to recognize that chemical formulas identify substances and used to determine the number of atoms of each element in chemical formulas by reading, and writing while completing notes and activity

1 Starter2. Notes3. Activity4. Exit

Ca (H2PO4)2 H

2O

NaCl

C2H4O2

Date Lecture/ Activity/ Lab Page9/25 Metal, Nonmetals, and Metalloids 41-429/26 Where’s Al? 43-449/27 Element Wanted Poster 45-469/30 Bohr Model Challenge 47-4810/1 Periodic Table Notes/Puzzles 49-5010/2 Periodic Table Chart 51-5210/3 Test Review 53-5410/8 Test Corrections 55-5610/9 Molecules, Compounds, and Elements 57-5810/10 Build a Molecule Activity 59-6010/15 Counting Atoms 61-6210/16 Counting Atoms with Coefficients 63-64

Table of Contents

Practice Chemical Formula

# of elements # of atoms

NaCl

CO2

C6H12

HgOH

Ag2S

Li2O

2

22

3

2 18

3 3

2 3

23

Application:Counting Atoms with

Coefficients

To determine the number of atoms present,

MULTIPLY the subscript by the coefficient

Example

The coefficient for this compound is 3

3MgCl2

There are:

1 x 3 = 3 Mg

2 x 3 = 6 Cl

“Double” Subscripts

Sometimes ions have a “double” subscript

4Al(NO2)3

One subscript is INSIDE the parenthesis and one

subscript is OUTSIDE the parenthesis

“Double” SubscriptsTo count the number of atoms in a

compound with “double” subscripts, you must MULTIPLY the subscripts

4Al2(CO2)3

There are:

2 x 4 = 8 Al atoms

3 x 1 x 4 = 12 C atoms

3 x 2 x 4 = 24 O atoms

Total atoms = 44

This “3” applies to both C and O

This “2” applies only to the O

Example

The coefficient for this compound is 5

5Mg(OH)2

There are:

1 x 5 = 5 Mg2+ ions

2 x 1 x 5 = 10 O atoms

2 x 1 x 5 = 10 H atoms

Total atoms = 25

More Examples

1. How many of each atom in Ba3(PO4)2?

2. How many of each atom in 4Ba3(PO4)2?

3. How many of each atom in Al2(Cr2O7)3?

4. How many of each atom in 2Al2(Cr2O7)3?

Answers

1. 3-Ba, 2-P, 8-0= 132. 12-Ba, 8-P, 32-O= 523. 2-Al, 6-Cr, 21-O= 294. 4-Al, 12-Cr, 42-O= 58

.

9/26/1164Counting Atoms with Coefficients

10/16/201363 Counting Atoms with Coefficient

10/16/2013

..

Starter:How many atoms are in the following compounds:

H2O, NaCl, Cl2

ApplicationHow many atoms1. Ba3(PO4)2

2. 4Ba3(PO4)2

3. Al2(Cr2O7)3

4. 2Al2(Cr2O7)3

Connection: Counting Atoms with Coefficients Ws Exit: What is the difference between a carbon dioxide (CO2) and carbon monoxide (CO)?.

Practice:

Chemical Formula

# of elements

# of atoms

NaCl

CO2

C6H12

HgOH

Ag2S

Li2O