counting atoms

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COUNTING ATOMS

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COUNTING ATOMS. RULES FOR COUNTING ATOMS. SUBSCRIPTS only refer to the atom that they are BEHIND . For example… H 2 S There are TWO atoms of HYDROGEN and only ONE atom of SULFUR. COEFFICIENTS. - PowerPoint PPT Presentation

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Page 1: COUNTING ATOMS

COUNTING ATOMS

Page 2: COUNTING ATOMS

RULES FOR COUNTING ATOMS

1. SUBSCRIPTS only refer to the atom that they are BEHIND. For example…

H2SThere are TWO atoms of HYDROGEN and only ONE atom of SULFUR.

Page 3: COUNTING ATOMS

COEFFICIENTS

2. COEFFICIENTS apply to the entire compound. You MULTIPLY the coefficients and SUBSCRIPTS.

2 H2S

ATOMS OF HYDROGEN:

ATOMS OF SULFUR:

4

2

IF THERE ISN’T A SUBSCRIPT BEHIND AN ELEMENT, ASSUME THERE IS ONLY ONE ATOM OF THAT ELEMENT!

Page 4: COUNTING ATOMS

PARENTHESES

3. If elements or compounds are inside of PARENTHESES, then the SUBSCRIPT behind the parentheses applies to everything inside.

Ba(OH)2

ATOMS OF BARIUM:

ATOMS OF OXYGEN:

ATOMS OF HYDROGEN:

1

2

2

Page 5: COUNTING ATOMS

LET’S PRACTICE!LET’S PRACTICE!

MgCl2

Atoms of Magnesium:

Atoms of Chlorine:

1

2

Al2S3

Atoms of Aluminum:

Atoms of Sulfur:

23

Page 6: COUNTING ATOMS

PRACTICEPRACTICE

H2SO4

Atoms of Hydrogen:Atoms of Sulfur:Atoms of Oxygen:

21

CH3OH

Atoms of Carbon:

Atoms of Hydrogen:

Atoms of Oxygen:

14

4

1

Page 7: COUNTING ATOMS

THIS COULD BE A LITTLE THIS COULD BE A LITTLE TRICKY…TRICKY…

Ca3(PO4)2 Atoms of Calcium:Atoms of Phosphorus:Atoms of Oxygen:

32

Al2(SO4)3

Atoms of Aluminum:

Atoms of Sulfur:

Atoms of Oxygen:

23

8

12

Page 8: COUNTING ATOMS

What about this BAD BOY???What about this BAD BOY???

2Ca3(PO4)2 Atoms of Calcium:Atoms of Phosphorus:Atoms of Oxygen:

64

16