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Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

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Page 1: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

Big Idea:

Given a chemical formula be able to count the number of atoms for each element in the compound or molecule.

Counting Atoms in Compounds or Molecules

Page 2: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

Parts of a Chemical Formula

2 H2O

4 Pb(OH)4

CoefficientSubscript

Element Symbol

Page 3: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

3 Parts of a Chemical Formula1. Chemical symbols

- Written in the order they appear on the periodic table, from left to right.

2. The subscript - Gives the number of atoms

- Must be written after the symbol, half size

3. The coefficient- Gives the number of compounds or molecules- Must be written regular size before the formula

Page 4: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

Counting AtomsRules for counting atoms in a molecule or compound.

1. A subscript shows how many atoms of that element are bonded in the molecule.

2. If there is no subscript then one atom of the element is present. Group all like atoms!!

3. If the subscript is outside the brackets, all the atoms inside the brackets are multiplied by the subscript outside the brackets.

4. Coefficients are multiplied last. The total number of atoms in the formula is multiplied by the coefficient.

Page 5: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

Count the Atoms

Oxygen – 1 atom

Hydrogen – 2 atoms

Formula - H2O

Page 6: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

Count the Atoms

Calcium – 1 atom

Oxygen – 2 atoms

Hydrogen – 2 atoms

Ca(OH)2

Page 7: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

CoefficientsThe number of water

molecules is shown with a coefficient.

Coefficients are written in front of the chemical formula.

3 H2O

Page 8: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

Count all the atoms

3 H2O

The coefficient multiplies all the atoms after it.

Hydrogen 3 x 2 = 6

Oxygen 3 x 1 = 3

Page 9: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

Test YourselfFormula Atom 1

presentHow Many?

Atom 2present

How Many?

Atom 3present

How Many?

Pb(OH)4

Mg3(PO3)2

As(IO4)5

2Cu(ClO2)2

1lead 4Oxygen 4Hydrogen

Page 10: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

Counting atomsFormula` Atom 1

presentHow Many?

Atom 2present

How Many?

Atom 3present

How Many?

Pb(OH)4

Mg3(PO3)2

As(IO4)5

2Cu(ClO2)2

4 4

3magnesium 2phosphorus 6oxygen

1arsenic 5iodine 20oxygen

2copper 4chlorine 8oxygen

lead 1 Oxygen Hydrogen

Page 11: Big Idea: Given a chemical formula be able to count the number of atoms for each element in the compound or molecule. Counting Atoms in Compounds or Molecules

Try Grouping Like Atoms

Given the formula CH3O(CH2)2OH

How many atoms of carbon in the formula?

3

How many atoms of oxygen in the formula?

2

How many atoms of hydrogen in the formula?

8